drm: mxsfb: Shutdown the display on system shutdown

When the system shuts down or warm reboots, the display may be active.
Implement the platform_driver .shutdown() operation and shut down the
display.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220101213755.506404-1-marex@denx.de

drivers/gpu/drm/mxsfb/mxsfb_drv.c

@@ -381,6 +381,13 @@ static int mxsfb_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static void mxsfb_shutdown(struct platform_device *pdev)
+{
+	struct drm_device *drm = platform_get_drvdata(pdev);
+
+	drm_atomic_helper_shutdown(drm);
+}
+
 #ifdef CONFIG_PM_SLEEP
 static int mxsfb_suspend(struct device *dev)
 {
@@ -404,6 +411,7 @@ static const struct dev_pm_ops mxsfb_pm_ops = {
 static struct platform_driver mxsfb_platform_driver = {
 	.probe		= mxsfb_probe,
 	.remove		= mxsfb_remove,
+	.shutdown	= mxsfb_shutdown,
 	.driver	= {
 		.name		= "mxsfb",
 		.of_match_table	= mxsfb_dt_ids,