Add inital xattr support for cgroups

If systemd is build with xattr support, it will try to mount the cgroup name systemd with xattr option.
Starting with systemd release v213 a failure on this mount is fatal and the system will not boot if it fails.
Arch Linux systemd is build with xattr support and so we cannot use this with sunxi-3.4 kernel.

Here backported (cherry-picked) patches to get initial xattr support for cgroups.

So we could use systemd for arm arch linux again.