bhyve: trap crb register of tpm devices

[corvink]

Summary

The crb emulation traps register
accesses and passes tpm commands to the tpm passthru emulation. The tpm
passthru emulation then takes the command, forwards it to the FreeBSD
tpm driver by accessing /dev/tpm0 and returns the result of the command
by reading back /dev/tpm0.

[markj]

usr.sbin/bhyve/tpm_intf_crb.c

502

Why not just write mr.name = "tpm_intf_crb";?

504

It would be nice to avoid duplicating this initialization with the paired register_mem() call.

505

I think we can assert that unregister_mem() does not fail.

[corvink]

This is a missing part of D40459.