drm/edid: add #defines and helpers for ELD

In the interest of reducing magic numbers and having to cross check with
the specs all the time.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 file changed