ext4: add the basic function for inline data support

Implement inline data with xattr.

Now we use "system.data" to store xattr, and the xattr will
be extended if the i_size is increased while we don't release
the space during truncate.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/ext4/Makefile
Simple merge

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/inline.c
Simple merge

diff --cc fs/ext4/inode.c
Simple merge

diff --cc fs/ext4/xattr.h
Simple merge