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_hdmi.c

@@ -2073,9 +2073,8 @@ static void intel_hdmi_destroy(struct drm_connector *connector)
 {
 	if (intel_attached_hdmi(connector)->cec_notifier)
 		cec_notifier_put(intel_attached_hdmi(connector)->cec_notifier);
-	kfree(to_intel_connector(connector)->detect_edid);
-	drm_connector_cleanup(connector);
-	kfree(connector);
+
+	intel_connector_destroy(connector);
 }
 
 static const struct drm_connector_funcs intel_hdmi_connector_funcs = {