gma500: Fix Poulsbo suspend/resume crash on devices with SDVO ports

Reported-by: Guillaume Clément <guillaume@baobob.org>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/gma500/psb_device.c

@@ -197,7 +197,8 @@ static int psb_save_display_registers(struct drm_device *dev)
 	}
 
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
-		connector->funcs->save(connector);
+		if (connector->funcs->save)
+			connector->funcs->save(connector);
 
 	mutex_unlock(&dev->mode_config.mutex);
 	return 0;
@@ -235,7 +236,8 @@ static int psb_restore_display_registers(struct drm_device *dev)
 			crtc->funcs->restore(crtc);
 
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
-		connector->funcs->restore(connector);
+		if (connector->funcs->restore)
+			connector->funcs->restore(connector);
 
 	mutex_unlock(&dev->mode_config.mutex);
 	return 0;