drm/i915/bios: Define VBT block 21 (EFP List) contents

Define the contents of VBT block 21 (EFP List). Specs are nowhere
to be found, but real world data suggests that each entry is just
the first four bytes of the EDID PnP ID structure.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-23-ville.syrjala@linux.intel.com


Acked-by: Jani Nikula <jani.nikula@intel.com>