f2fs: add missing part of patch "f2fs: support flexible inline xattr size"

I found that "f2fs: support flexible inline xattr size" had been merge half part in android-4.14-p and lose another half part, so fix it.

"f2fs: support flexible inline xattr size" is here and it had been merge into android-4.14

- https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/fs/f2fs/inode.c?h=dev&id=6afc662e68b5f988282ff20afd58a89b1c279dca



but in android-4.14-p, the merge list is strange, I don't know why....

if you list the merge message of f2fs/inode.c, you can see below in android-4.14-p

8629d9bd Merge 4.14.86 into android-4.14-p by Greg Kroah-Hartman ¡€ 8 weeks ago ASB-2018-12-05_4.14-p => have a half of "f2fs: support flexible inline xattr size"
....
9e6c4a85 f2fs: clean up with is_valid_blkaddr() by Chao Yu ¡€ 8 months ago  => don't have
818299f6 Merge 4.14.56 into android-4.14 by Greg Kroah-Hartman ¡€ 6 months ago => patch is ok
eab3a341 f2fs: give message and set need_fsck given broken node id by Jaegeuk Kim => don't have

Now, this missing patch will result in SW FBE reboot fail

Signed-off-by: Peng Zhou <peng.zhou@mediatek.com>