dm: update stale comment in end_clone_bio()

Since commit a1ce35fa ("block: remove dead elevator
code") blk_end_request() has been replaced with blk_mq_end_request().
So update comment to reference blk_mq_end_request() accordingly.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-rq.c

@@ -115,7 +115,7 @@ static void end_clone_bio(struct bio *clone)
 
 	/*
 	 * Update the original request.
-	 * Do not use blk_end_request() here, because it may complete
+	 * Do not use blk_mq_end_request() here, because it may complete
 	 * the original request before the clone, and break the ordering.
 	 */
 	if (is_last)