drm/i915/lvds: Always use the presence pin for LVDS on PCH

With the introduction of the PCH, we gained an LVDS presence pin but we
continued to use the existing logic that asserted that LVDS was only
supported on certain mobile chipsets. However, there are desktop
IronLake systems with LVDS attached which we fail to detect. So for PCH,
trust the LVDS presence pin and quirk all the lying manufacturers.

Tested-by: Daniel Woff <wolff.daniel@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43171


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>