drm/i915: Ignore VBT backlight presence check on HP Chromebook 14

commit c675949e
    drm/i915: do not setup backlight if not available according to VBT

caused a regression on the HP Chromebook 14 (with Celeron 2955U CPU),
which has a misconfigured VBT. Apply quirk to ignore the VBT backlight
presence check during backlight setup.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79813


Signed-off-by: Scot Doyle <lkml14@scotdoyle.com>
Tested-by: Stefan Nagy <public@stefan-nagy.at>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>