This uses a LZMA compressed U-Boot FIT image for the NanoPi R2S. This
way, the resulting sysupgrade image uses ~1M les space compared to using
an uncompressed kernel.
Signed-off-by: David Bauer <mail@david-bauer.net>
This refactors the sysupgrade image generation code to make it reusable
for all devices generating an SD card image.
While at it, move the bootscripts to their own subdirectory.
Signed-off-by: David Bauer <mail@david-bauer.net>