blk-mq: fix allocation of set->tags

type of set->tags is struct blk_mq_tags **.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5fbbb22..c277797 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1537,7 +1537,8 @@
 		return -EINVAL;
 
 
-	set->tags = kmalloc_node(set->nr_hw_queues * sizeof(struct blk_mq_tags),
+	set->tags = kmalloc_node(set->nr_hw_queues *
+				 sizeof(struct blk_mq_tags *),
 				 GFP_KERNEL, set->numa_node);
 	if (!set->tags)
 		goto out;