virtio-pmem not working on microvm: virtio-pmem missing request data
Description of problem:
When using micorvm, qemu does not "connect" the memory backend mem1 with the pmem device. 

When using the first command is executed, qemu shows the following starts message:
```
qemu-system-x86_64: virtio-pmem missing request data 
```

and the kernel outputs following messages:
```
[    0.043871] nd_pmem namespace0.0: could not reserve region [mem 0x00000000-0x001fffff]
[    0.043923] IPI shorthand broadcast: enabled
[    0.044022] nd_pmem: probe of namespace0.0 failed with error -16
```