f2fs: fix to dirty inode synchronously

If user change inode's i_flags via ioctl, let's add it into global
dirty list, so that checkpoint can guarantee its persistence before
fsync, it can make checkpoint keeping strong consistency.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>