drm/i915: assume all GM45 Acer laptops use inverted backlight PWM

drm/i915: assume all GM45 Acer laptops use inverted backlight PWM

There is plenty of evidence suggesting all of the GM45 based Acer
laptops (including their eMachines and Packard Bell brands) use inverted
backlight PWM. Assume this is really the case, and quirk them all.

The old bugs that were fixed by subsystem device specific quirks:
 * https://bugs.freedesktop.org/show_bug.cgi?id=59628
 * https://bugzilla.kernel.org/show_bug.cgi?id=31522#c35
 * https://bugs.freedesktop.org/show_bug.cgi?id=44156
 * https://bugzilla.kernel.org/show_bug.cgi?id=53881

See also this bug and the plethora of duplicates:
 * https://bugs.launchpad.net/ubuntu/+source/linux/+bug/765438

References: https://bugzilla.kernel.org/show_bug.cgi?id=54171
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>