instruction: 0.827
runtime: 0.117
syscall: 0.056



m68k: fpu: fsave/frestore should be enabled for 68020/68030
Description of problem:
valid 68020/68030 code can use `fsave`/`frestore` instructions to save/restore the state of an external 68881/68882 but currently QEMU only allows these instructions on 68040 and everyone else gets an f-line exception.

I guess something like this to allow frestore/fsave. m68k programmers reference manual says they are 68881/68882/68040 and there don's seem to be any differences.

``` diff
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index d5d2322329..92dc9d8563 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -5455,7 +5455,7 @@ DISAS_INSN(frestore)
         gen_exception(s, s->base.pc_next, EXCP_PRIVILEGE);
         return;
     }
-    if (m68k_feature(s->env, M68K_FEATURE_M68040)) {
+    if (m68k_feature(s->env, M68K_FEATURE_FPU)) {
         SRC_EA(env, addr, OS_LONG, 0, NULL);
         /* FIXME: check the state frame */
     } else {
@@ -5472,7 +5472,7 @@ DISAS_INSN(fsave)
         return;
     }
 
-    if (m68k_feature(s->env, M68K_FEATURE_M68040)) {
+    if (m68k_feature(s->env, M68K_FEATURE_FPU)) {
         /* always write IDLE */
         TCGv idle = tcg_constant_i32(0x41000000);
         DEST_EA(env, insn, OS_LONG, idle, NULL);
```