drm: rcar-du: Use generic drm_connector_register_all() helper

Now that a generic drm_connector_register_all() helper exists we may safely
substitute it for the driver-specific implementation of connectors plugging
in sysfs.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: linux-renesas-soc@vger.kernel.org
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1461068693-11260-4-git-send-email-abrodkin@synopsys.com

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

@@ -361,14 +361,7 @@ static int rcar_du_probe(struct platform_device *pdev)
 	if (ret)
 		goto error;
 
-	mutex_lock(&ddev->mode_config.mutex);
-	drm_for_each_connector(connector, ddev) {
-		ret = drm_connector_register(connector);
-		if (ret < 0)
-			break;
-	}
-	mutex_unlock(&ddev->mode_config.mutex);
-
+	ret = drm_connector_register_all(ddev);
 	if (ret < 0)
 		goto error;