drm: rcar-du: Shutdown the display on remove

When the device is unbound from the driver (the DU being a platform
device, this occurs either when removing the DU module, or when
unbinding the device manually through sysfs), the display may be active.
Make sure it gets shut down.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -553,6 +553,7 @@ static int rcar_du_remove(struct platform_device *pdev)
 	struct drm_device *ddev = &rcdu->ddev;
 
 	drm_dev_unregister(ddev);
+	drm_atomic_helper_shutdown(ddev);
 
 	drm_kms_helper_poll_fini(ddev);