mkimage.sh.in: odroid-c2: u-boot doesn't understand new ext4 features, disable.
mkrootfs.sh.in: add odroid-c2.
mkrootfs.sh.in: fix for odroid-c2.
mkimage.sh: fix sfdisk usage for multiple arches.
mkimage.sh.in: add odroid-c2.
[random] can be seeded with 0