blk-mq: avoid re-initialize request which is failed in direct dispatch

If we directly issue a request and it fails, we use
blk_mq_merge_queue_io(). But we already assigned bio to a request in
blk_mq_bio_to_request. blk_mq_merge_queue_io shouldn't run
blk_mq_bio_to_request again.
Signed-off-by: NShaohua Li <shli@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -1284,6 +1284,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 				blk_mq_end_request(rq, rq->errors);
 				goto done;
 			}
+			blk_mq_insert_request(rq, false, true, true);
+			return;
 		}
 	}