btrfs: fix csum assert to check objectid of the root

In the future we may have multiple csum roots, so simply check the
objectid is for a csum root instead of checking against ->csum_root.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/file-item.c

@@ -801,7 +801,7 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
 	const u32 csum_size = fs_info->csum_size;
 	u32 blocksize_bits = fs_info->sectorsize_bits;
 
-	ASSERT(root == fs_info->csum_root ||
+	ASSERT(root->root_key.objectid == BTRFS_CSUM_TREE_OBJECTID ||
 	       root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID);
 
 	path = btrfs_alloc_path();