There were two instances of code to control the panel backlight and
neither handled the complete set of device variations.
Fixes:
Bug 29716 - [GM965] Regression: Backlight resets to minimum when changing resolution
https://bugs.freedesktop.org/show_bug.cgi?id=29716
And a bug on one of my PineView boxes which overflowed the backlight
value.
Incorporates part of a similar patch by Matthew Garrett that exposes a
native Intel backlight controller.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
a957355693