[PATCH] block: fix noderef.cocci warnings

From: kbuild test robot <redacted>

block/genhd.c:1483:37-43: ERROR: application of sizeof to pointer

 sizeof when applied to a pointer typed expression gives the size of
 the pointer

Generated by: scripts/coccinelle/misc/noderef.cocci

Fixes: b4032d402850 ("block: Introduce alloc_disk_node_attr()")
Signed-off-by: kbuild test robot <redacted>
---

 genhd.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/genhd.c
+++ b/block/genhd.c

@@ -1480,7 +1480,7 @@ struct gendisk *__alloc_disk_node(int mi
 		disk_to_dev(disk)->class = &block_class;
 		disk_to_dev(disk)->type = &disk_type;
 		if (num_groups) {
-			memcpy(disk->ag, ag, num_groups * sizeof(ag));
+			memcpy(disk->ag, ag, num_groups * sizeof(*ag));
 			disk_to_dev(disk)->groups = disk->ag;
 		}
 		device_initialize(disk_to_dev(disk));