bhyve: support queue configuration for NVMe disks

bhyve: support queue configuration for NVMe disks

bhyve supports queue configuration for the NVMe disks:

  maxq        Max number of queues.
  qsz         Max elements in each queue.

Map that to the disk driver's "queues" and "queue_size" attributes
respectfully, so:

  <driver name='file' type='raw' queues='2' queue_size='256'/>

results in:

  -s N:0,nvme,/tmp/disk.img,maxq=2,qsz=256

Signed-off-by: Roman Bogorodskiy <bogorodskiy@gmail.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>