drm/i915: give up on 8xx lid status

These old machines more often than not lie about their lid state.  So
don't use it to detect LVDS presence, but leave the event handler to
deal with lid open/close, when we might need to reset the mode.

Fixes kernel bug #15248

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@kernel.org
Signed-off-by: Eric Anholt <eric@anholt.net>