blk-mq: let blk_mq_tag_to_rq() take blk_mq_tags as the main parameter

We currently pass in the hardware queue, and get the tags from there.
But from scsi-mq, with a shared tag space, it's a lot more convenient
to pass in the blk_mq_tags instead as the hardware queue isn't always
directly available. So instead of having to re-map to a given
hardware queue from rq->mq_ctx, just pass in the tags structure.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index abc858b..74abd49 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -193,7 +193,9 @@
 static struct request *mtip_rq_from_tag(struct driver_data *dd,
 					unsigned int tag)
 {
-	return blk_mq_tag_to_rq(dd->queue->queue_hw_ctx[0], tag);
+	struct blk_mq_hw_ctx *hctx = dd->queue->queue_hw_ctx[0];
+
+	return blk_mq_tag_to_rq(hctx->tags, tag);
 }
 
 static struct mtip_cmd *mtip_cmd_from_tag(struct driver_data *dd,