Draft: image-rpi64: Add device tree overlay for rpi 7inch touchscreen
u-boot is now able to detect the rpi 7inch touchscreen automatically and load a device tree overlay if needed.
Make sure that overlay is installed at the right place.
Draft: This depends on the kernel changes in: pkg/linux!200
u-boot changes in pkg/u-boot!80 are necessary for the detection to work, but not needed for building the images, so that is not blocking.