[media] dvb core: must check dvb_create_media_graph()

If media controller is enabled and mdev is filled, it should
ensure that the media graph will be properly initialized.

Enforce that.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/dvb-usb-v2/dvb_usb_core.c

@@ -698,7 +698,9 @@ static int dvb_usbv2_adapter_frontend_init(struct dvb_usb_adapter *adap)
 		}
 	}
 
-	dvb_create_media_graph(&adap->dvb_adap);
+	ret = dvb_create_media_graph(&adap->dvb_adap);
+	if (ret < 0)
+		goto err_dvb_unregister_frontend;
 
 	return 0;