bhyve nvme: Support minimal Controller list

[chuck]

Summary

Controllers must support the Identify Controller list if they support
Namespace Management. But the UNH NVMe tests use this command regardless
of whether the device under test supports Namespace Management.

This implementation returns an empty Controller list (i.e., Number of
Identifiers is zero).

Fixes UNH Test 1.1.2

[jhb]

usr.sbin/bhyve/pci_nvme.c

1540

For new code I prefer memset since it is POSIX unlike bzero.

[chuck]

Switch bzero to memset