drm/i915: debug log when GMD ID indicates there's no display

Debug log similar to the device id based identification of no display.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230804084600.1005818-2-jani.nikula@intel.com