blk-mq: remember to start timeout handler for direct queue

Commit 07068d5b8e added a direct-to-hw-queue mode, but this mode
needs to remember to add the request timeout handler as well.
Without it, we don't track timeouts for these requests.

Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -1217,6 +1217,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
 		blk_mq_bio_to_request(rq, bio);
 		blk_mq_start_request(rq, true);
+		blk_add_timer(rq);
 
 		/*
 		 * For OK queue, we are done. For error, kill it. Any other