blk-mq: factor out a helper to iterate all tags for a request_queue

And replace the blk_mq_tag_busy_iter with it - the driver use has been
replaced with a new helper a while ago, and internal to the block we
only need the new version.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2306330..7785ae96 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -641,24 +641,16 @@
 		.next		= 0,
 		.next_set	= 0,
 	};
-	struct blk_mq_hw_ctx *hctx;
 	int i;
 
-	queue_for_each_hw_ctx(q, hctx, i) {
-		/*
-		 * If not software queues are currently mapped to this
-		 * hardware queue, there's nothing to check
-		 */
-		if (!blk_mq_hw_queue_mapped(hctx))
-			continue;
-
-		blk_mq_tag_busy_iter(hctx, blk_mq_check_expired, &data);
-	}
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
 
 	if (data.next_set) {
 		data.next = blk_rq_timeout(round_jiffies_up(data.next));
 		mod_timer(&q->timeout, data.next);
 	} else {
+		struct blk_mq_hw_ctx *hctx;
+
 		queue_for_each_hw_ctx(q, hctx, i) {
 			/* the hctx may be unmapped, so check it here */
 			if (blk_mq_hw_queue_mapped(hctx))