drm/i915: Ignore VBT backlight check on Macbook 2, 1

drm/i915: Ignore VBT backlight check on Macbook 2, 1

commit c675949ec58ca50d5a3ae3c757892f1560f6e896
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

prevents backlight setup on Macbook 2,1. Apply quirk to ignore the VBT
check so backlight is set up properly.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81438
Signed-off-by: Jens Stein Jørgensen <jens.s.stein@gmail.com>
Cc: stable@vger.kernel.org (3.15+)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>