drm/i915/opregion: add support for mailbox #5 EDID Based on original patch series by: Jani Nikula <jani.nikula@intel.com> Cc: Jani Nikula <jani.nikula@intel.com> Co-developed-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com>