f2fs: add missing f2fs_balance_fs in __recover_dot_dentries

__recover_do_dentries will try to grab free space in storage, so fix to
add missing f2fs_balance_fs here.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>