ubi_sysupgrade app

see patch description for details

initial release

This is a modified u-boot code repository for the AVM Fritz!Box 4040.
This code was taken from ASUS' RT-AC58U GPL archive.

Note: The generated uboot-fritz4040.bin will not replace the EVA loader.
Instead, eva will chainload u-boot. This makes it possible to use AVM's
firmware restore utility to reflash the original firmware.