Unnecessary lock is taken. ring lock should be sufficient to protect the
work queue submission.

This was noticed when doing performance testing. The hbalock is not
needed to issue io to the nvme work queue.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>