SnapAdreno 9cc1e92 (branch backlight-path, not pushed): AdrenoBacklight
maps nits proportionally onto levels with the compat helpers of the
previous commit, publishes force-brightness-control so WindowServer's
BrightnessControl writes brightness-nits to it, and publishes its
DPCD700 diagnostic as 64 bits. The default kext is section for section
the base commit's.