Check for ACPI backlight support otherwise use vendor ACPI drivers - version 4

Thomas Renninger
2008-08-01T15:38:08Z

Modifications to version 3:
- Stop checking for backlight capabilities on devices which cannot
be a video device (thanks to Peter <nokos@gmx.net>
- Do not stop checking on the first video device which has no backlight
support (many thanks to Peter <nokos@gmx.net>
- Removed a half wrong comment, found by Zhang Rui.

Please queue for 2.6.28.
Tell me if parts do not patch and I can repost them against
whatever is needed.

Ideally they should go in together with Matthew's/Hong's IGD
patches (which should come mainline through the dri tree), these
patches should need mine.