Btrfs: fix check_int 'leaf item out of bounce' regression

Yet another cleanup patch broke code for which no xfstest exists.
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/check-integrity.c

@@ -1038,7 +1038,7 @@ static int btrfsic_process_metablock(
 						     disk_item_offset,
 						     sizeof(struct btrfs_item));
 			item_offset = btrfs_stack_item_offset(&disk_item);
-			item_size = btrfs_stack_item_offset(&disk_item);
+			item_size = btrfs_stack_item_size(&disk_item);
 			disk_key = &disk_item.key;
 			type = btrfs_disk_key_type(disk_key);