btrfs: Opencode ordered_data_tree_panic

It's a simple wrapper over btrfs_panic and is called only once. Just
open code it.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>