f2fs: add flags for inline xattrs

This patch adds basic inode flags for inline xattrs, F2FS_INLINE_XATTR,
and add a mount option, inline_xattr, which is enabled when xattr is set.

If the mount option is enabled, all the files are marked with the inline_xattrs
flag.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

diff --cc fs/f2fs/f2fs.h
Simple merge

diff --cc fs/f2fs/inode.c
Simple merge

diff --cc fs/f2fs/super.c
Simple merge

diff --cc include/linux/f2fs_fs.h
Simple merge