block: use bool as the return type of elv_iosched_allow_bio_merge

We have bool type now, update the old signature.
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/0db0a0298758d60d0f4df8b7126ac6a381e5a5bb.1669736350.git.nickyc975@zju.edu.cnSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/elevator.c

@@ -57,7 +57,7 @@ static LIST_HEAD(elv_list);
  * Query io scheduler to see if the current process issuing bio may be
  * merged with rq.
  */
-static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
+static bool elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
 {
 	struct request_queue *q = rq->q;
 	struct elevator_queue *e = q->elevator;
@@ -65,7 +65,7 @@ static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
 	if (e->type->ops.allow_merge)
 		return e->type->ops.allow_merge(q, rq, bio);
 
-	return 1;
+	return true;
 }
 
 /*