blk-mq: fix the blk_mq_add_to_requeue_list call in blk_kick_flush

Commit b12e5c6c accidentally changes blk_kick_flush to do a head
insert into the requeue list, fix this up.

Fixes: b12e5c6c ("blk-mq: pass a flags argument to blk_mq_add_to_requeue_list")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230416073553.966161-1-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-flush.c

@@ -346,7 +346,7 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
 	smp_wmb();
 	req_ref_set(flush_rq, 1);
 
-	blk_mq_add_to_requeue_list(flush_rq, BLK_MQ_INSERT_AT_HEAD);
+	blk_mq_add_to_requeue_list(flush_rq, 0);
 	blk_mq_kick_requeue_list(q);
 }