There's no callers in-tree anymore since commit 64403612 ("btrfs:
rework btrfs_check_space_for_delayed_refs")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>