drm/{i915, xe}: deduplicate plane_config_fini() between i915 and xe
Move the common code to display. Retain empty xe_plane_config_fini() for
now, in case it's needed in the future.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/14322386cdb1a0f4f6c7ff74a5a9696ea0ff84bf.1765812266.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>