NVMe: Free admin queue memory on initialisation failure

If the adapter fails initialisation, the memory allocated for the
admin queue may not be freed.  Split the memory freeing part of
nvme_free_queue() into nvme_free_queue_mem() and call it in the case of
initialisation failure.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>