ACPI / video: update video_extension.txt for backlight control
ACPI / video: update video_extension.txt for backlight control

The ACPI video driver has changed a lot, and it doesn't export
interfaces in /proc any more, so the documentation for it should
be updated.

This update focuses on ACPI video driver's backlight control.

Signed-off-by: Aaron Lu <e835aaae27ef45c770cbc83733586d01aadc3a43@intel.com>
Signed-off-by: Rafael J. Wysocki <27ffc44a8ec6a212fba98cfc3246c6ce8ab131e0@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs