drm/i915/opregion: convert intel_opregion_get_edid() to struct drm_edid

Simplify validation and use by converting to drm_edid.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/6abb01f1e97d54a3c11bec24377f035df412b492.1674643465.git.jani.nikula@intel.com