drm/i915: add a common connector type independent destroy hook

Almost all of the connector destroy functions do the same thing. The
differences are in the edid, detect_edid and panel cleanups, but those
are safely NULL when not initialized. Roll out a common connector
destroy hook.

Inspired by commit bc3213c444 ("drm/i915: Drop the eDP check from
intel_dp_connector_destroy()").

Cc: Ville Syrjala <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/20181009141103.20387-1-jani.nikula@intel.com

drivers/gpu/drm/i915/intel_tv.c

@@ -1377,17 +1377,10 @@ intel_tv_get_modes(struct drm_connector *connector)
 	return count;
 }
 
-static void
-intel_tv_destroy(struct drm_connector *connector)
-{
-	drm_connector_cleanup(connector);
-	kfree(connector);
-}
-
 static const struct drm_connector_funcs intel_tv_connector_funcs = {
 	.late_register = intel_connector_register,
 	.early_unregister = intel_connector_unregister,
-	.destroy = intel_tv_destroy,
+	.destroy = intel_connector_destroy,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,