bhyve nvme: Fix Controller init error cases

bhyve nvme: Fix Controller init error cases

Fuzzing of bhyve uncovered an assertion failure in the NVMe emulation.
Investigation uncovered several corner cases the code did not handle.
This change handles several Controller initialization errors, including
 - bad AQ sizes
 - bad AQ vm_map_gpa
 - doorbell writes prior to RDY
 - doorbell writes to uninitialized queue
 - CSTS.RDY if CFS set

PR:		256317,256319,256320,256322
Reported by:	Cheolwoo Myung <cwmyung@snu.ac.kr>
Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D35453