dsl-vrx200-firmware-xdsl: create Lantiq vrx200 firmware patches

Instead of having two big binaries only add one binary and then a patch
to create the other one when needed at runtime.
This is easier to handle in one Makefile for both firmware files.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
SVN-Revision: 48939