MFC r293328:

MFC r293328:

  nvme: do not revert to single I/O queue when per-CPU queues not available

  Previously nvme(4) would revert to a single I/O queue if it could not
  allocate enought interrupt vectors or NVMe submission/completion queues
  to have one I/O queue per core.  This patch determines how to utilize a
  smaller number of available interrupt vectors, and assigns (as closely
  as possible) an equal number of cores to each associated I/O queue.

git-svn-id: svn://svn.freebsd.org/base/stable/10@293671 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f