blk-merge: kill dead queue lock held check

This is dead code, any queue reaching this part has mq_ops
attached.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -729,9 +729,6 @@ enum elv_merge blk_try_req_merge(struct request *req, struct request *next)
 static struct request *attempt_merge(struct request_queue *q,
 				     struct request *req, struct request *next)
 {
-	if (!q->mq_ops)
-		lockdep_assert_held(q->queue_lock);
-
 	if (!rq_mergeable(req) || !rq_mergeable(next))
 		return NULL;