Abort in lan9118_16bit_mode_[read|write]()
Description of problem:
[read|write][w|l] are allowed but [read|write]b are not allowed when mode_16bit is enabled.
Steps to reproduce:
```
export QEMU=/path/to/qemu-system-arm

cat << EOF | $QEMU \
-machine smdkc210 -monitor none -serial none \
-display none -qtest stdio
readb 0x5000070
EOF
```
Additional information:
```
==1940==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
INFO: found LLVMFuzzerCustomMutator (0x5654b8eede90). Disabling -len_control by default.
INFO: Running with entropic power schedule (0xFF, 100).
INFO: Seed: 3248453476
INFO: Loaded 1 modules   (601357 inline 8-bit counters): 601357 [0x5654bbdd8000, 0x5654bbe6ad0d), 
INFO: Loaded 1 PC tables (601357 PCs): 601357 [0x5654bb4aa340,0x5654bbdd7410), 
./qemu-videzzo-arm-target-videzzo-fuzz-lan9118: Running 1 inputs 1 time(s) each.
INFO: Reading pre_seed_input if any ...
INFO: Executing pre_seed_input if any ...
INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes
Matching objects by name , *lan9118-mmio*
This process will fuzz the following MemoryRegions:
  * lan9118-mmio[0] (size 100)
This process will fuzz through the following interfaces:
  * clock_step, EVENT_TYPE_CLOCK_STEP, 0xffffffff +0xffffffff, 255,255
  * lan9118-mmio, EVENT_TYPE_MMIO_READ, 0x5000000 +0x100, 1,4
  * lan9118-mmio, EVENT_TYPE_MMIO_WRITE, 0x5000000 +0x100, 1,4
INFO: A corpus is not provided, starting from an empty corpus
#2      INITED cov: 3 ft: 4 corp: 1/1b exec/s: 0 rss: 221Mb
Running: ./crash-663e5408ee573b1e9d073c796ffbaaae9bd583cb
qemu: hardware error: lan9118_read: Bad size 0x1

CPU #0:
R00=00000000 R01=00000000 R02=00000000 R03=00000000
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00000000
R12=00000000 R13=00000000 R14=00000000 R15=00000000
PSR=400001d3 -Z-- A svc32
s00=00000000 s01=00000000 d00=0000000000000000
s02=00000000 s03=00000000 d01=0000000000000000
s04=00000000 s05=00000000 d02=0000000000000000
s06=00000000 s07=00000000 d03=0000000000000000
s08=00000000 s09=00000000 d04=0000000000000000
s10=00000000 s11=00000000 d05=0000000000000000
s12=00000000 s13=00000000 d06=0000000000000000
s14=00000000 s15=00000000 d07=0000000000000000
s16=00000000 s17=00000000 d08=0000000000000000
s18=00000000 s19=00000000 d09=0000000000000000
s20=00000000 s21=00000000 d10=0000000000000000
s22=00000000 s23=00000000 d11=0000000000000000
s24=00000000 s25=00000000 d12=0000000000000000
s26=00000000 s27=00000000 d13=0000000000000000
s28=00000000 s29=00000000 d14=0000000000000000
s30=00000000 s31=00000000 d15=0000000000000000
s32=00000000 s33=00000000 d16=0000000000000000
s34=00000000 s35=00000000 d17=0000000000000000
s36=00000000 s37=00000000 d18=0000000000000000
s38=00000000 s39=00000000 d19=0000000000000000
s40=00000000 s41=00000000 d20=0000000000000000
s42=00000000 s43=00000000 d21=0000000000000000
s44=00000000 s45=00000000 d22=0000000000000000
s46=00000000 s47=00000000 d23=0000000000000000
s48=00000000 s49=00000000 d24=0000000000000000
s50=00000000 s51=00000000 d25=0000000000000000
s52=00000000 s53=00000000 d26=0000000000000000
s54=00000000 s55=00000000 d27=0000000000000000
s56=00000000 s57=00000000 d28=0000000000000000
s58=00000000 s59=00000000 d29=0000000000000000
s60=00000000 s61=00000000 d30=0000000000000000
s62=00000000 s63=00000000 d31=0000000000000000
FPSCR: 00000000
CPU #1:
R00=00000000 R01=00000000 R02=00000000 R03=00000000
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00000000
R12=00000000 R13=00000000 R14=00000000 R15=00000000
PSR=400001d3 -Z-- A svc32
s00=00000000 s01=00000000 d00=0000000000000000
s02=00000000 s03=00000000 d01=0000000000000000
s04=00000000 s05=00000000 d02=0000000000000000
s06=00000000 s07=00000000 d03=0000000000000000
s08=00000000 s09=00000000 d04=0000000000000000
s10=00000000 s11=00000000 d05=0000000000000000
s12=00000000 s13=00000000 d06=0000000000000000
s14=00000000 s15=00000000 d07=0000000000000000
s16=00000000 s17=00000000 d08=0000000000000000
s18=00000000 s19=00000000 d09=0000000000000000
s20=00000000 s21=00000000 d10=0000000000000000
s22=00000000 s23=00000000 d11=0000000000000000
s24=00000000 s25=00000000 d12=0000000000000000
s26=00000000 s27=00000000 d13=0000000000000000
s28=00000000 s29=00000000 d14=0000000000000000
s30=00000000 s31=00000000 d15=0000000000000000
s32=00000000 s33=00000000 d16=0000000000000000
s34=00000000 s35=00000000 d17=0000000000000000
s36=00000000 s37=00000000 d18=0000000000000000
s38=00000000 s39=00000000 d19=0000000000000000
s40=00000000 s41=00000000 d20=0000000000000000
s42=00000000 s43=00000000 d21=0000000000000000
s44=00000000 s45=00000000 d22=0000000000000000
s46=00000000 s47=00000000 d23=0000000000000000
s48=00000000 s49=00000000 d24=0000000000000000
s50=00000000 s51=00000000 d25=0000000000000000
s52=00000000 s53=00000000 d26=0000000000000000
s54=00000000 s55=00000000 d27=0000000000000000
s56=00000000 s57=00000000 d28=0000000000000000
s58=00000000 s59=00000000 d29=0000000000000000
s60=00000000 s61=00000000 d30=0000000000000000
s62=00000000 s63=00000000 d31=0000000000000000
FPSCR: 00000000
==1940== ERROR: libFuzzer: deadly signal
    #0 0x5654b48090fe in __sanitizer_print_stack_trace /root/llvm-project/compiler-rt/lib/asan/asan_stack.cpp:86:3
    #1 0x5654b4757d71 in fuzzer::PrintStackTrace() /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:38
    #2 0x5654b4730ca6 in fuzzer::Fuzzer::CrashCallback() (.part.0) /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:236:18
    #3 0x5654b4730d72 in fuzzer::Fuzzer::CrashCallback() /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:208:1
    #4 0x5654b4730d72 in fuzzer::Fuzzer::StaticCrashSignalCallback() /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:207:19
    #5 0x7fb6db17941f  (/lib/x86_64-linux-gnu/libpthread.so.0+0x1441f)
    #6 0x7fb6daf8b00a in __libc_signal_restore_set /build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/internal-signals.h:86:3
    #7 0x7fb6daf8b00a in raise /build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/raise.c:48:3
    #8 0x7fb6daf6a858 in abort /build/glibc-SzIz7B/glibc-2.31/stdlib/abort.c:79:7
    #9 0x5654b483964a in __wrap_abort /root/videzzo/videzzo_qemu/qemu/build-san-6/../tests/qtest/videzzo/less_crashes_wrappers.c:24:12
    #10 0x5654b6a64d84 in hw_error /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/cpus.c:128:5
    #11 0x5654b5ac50c7 in lan9118_16bit_mode_read /root/videzzo/videzzo_qemu/qemu/build-san-6/../hw/net/lan9118.c:1319:5
    #12 0x5654b7ee045b in memory_region_read_accessor /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/memory.c:440:11
    #13 0x5654b7ea0761 in access_with_adjusted_size /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/memory.c:554:18
    #14 0x5654b7e9db2c in memory_region_dispatch_read1 /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/memory.c:1424:16
    #15 0x5654b7e9d268 in memory_region_dispatch_read /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/memory.c:1457:9
    #16 0x5654b7f1946d in flatview_read_continue /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/physmem.c:2892:23
    #17 0x5654b7f1aa78 in flatview_read /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/physmem.c:2934:12
    #18 0x5654b7f1a538 in address_space_read_full /root/videzzo/videzzo_qemu/qemu/build-san-6/../softmmu/physmem.c:2947:18
    #19 0x5654b483a7ea in address_space_read /root/videzzo/videzzo_qemu/qemu/include/exec/memory.h:2869:18
    #20 0x5654b483a7ea in qemu_readb /root/videzzo/videzzo_qemu/qemu/build-san-6/../tests/qtest/videzzo/videzzo_qemu.c:1010:5
    #21 0x5654b483997e in dispatch_mmio_read /root/videzzo/videzzo_qemu/qemu/build-san-6/../tests/qtest/videzzo/videzzo_qemu.c:1034:35
    #22 0x5654b8ee984f in videzzo_dispatch_event /root/videzzo/videzzo.c:1122:5
    #23 0x5654b8ee0bcb in __videzzo_execute_one_input /root/videzzo/videzzo.c:272:9
    #24 0x5654b8ee0aa0 in videzzo_execute_one_input /root/videzzo/videzzo.c:313:9
    #25 0x5654b48500fc in videzzo_qemu /root/videzzo/videzzo_qemu/qemu/build-san-6/../tests/qtest/videzzo/videzzo_qemu.c:1497:12
    #26 0x5654b8eee132 in LLVMFuzzerTestOneInput /root/videzzo/videzzo.c:1891:18
    #27 0x5654b4731816 in fuzzer::Fuzzer::ExecuteCallback(unsigned char*, unsigned long) /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:594:17
    #28 0x5654b4714444 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:323:21
    #29 0x5654b471f3ee in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char*, unsigned long)) /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:885:19
    #30 0x5654b470b9d6 in main /root/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:30
    #31 0x7fb6daf6c082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16
    #32 0x5654b470ba2d in _start (/root/videzzo/videzzo_qemu/out-san/qemu-videzzo-arm-target-videzzo-fuzz-lan9118+0x300da2d)

NOTE: libFuzzer has rudimentary signal handlers.
      Combine libFuzzer with AddressSanitizer or similar for better crash reports.
SUMMARY: libFuzzer: deadly signal
MS: 0 ; base unit: 0000000000000000000000000000000000000000
0x4,0x2,0x29,0x92,0xa,0x0,0x0,0x0,0x0,0x0,0x0,0x8,0x70,0x0,0x0,0x5,0x0,0x0,0x0,0x0,0x1,0x0,0x0,0x0,0x1,0x9,0x48,0x0,0x0,0x5,0x0,0x0,0x0,0x0,0x4,0x0,0x0,0x0,0x29,0x1f,0x8e,0x23,0x0,0x0,0x0,0x0,
\x04\x02)\x92\x0a\x00\x00\x00\x00\x00\x00\x08p\x00\x00\x05\x00\x00\x00\x00\x01\x00\x00\x00\x01\x09H\x00\x00\x05\x00\x00\x00\x00\x04\x00\x00\x00)\x1f\x8e#\x00\x00\x00\x00
```