Add function needed to generate ACPI backlight control SSDT, along with
Kconfig values for accessing the registers.
Tested by adding gfx register on system76/gaze16 and booting Windows.
Display settings has a brightness setting, and can change the brightness
level.
Change-Id: Id8b14c0b4a7a681dc6cb95778c12a006a7e31373
Signed-off-by: Tim Crawford <tcrawford@system76.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57823
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1724b57729