[media] dvb_usb_v2: fix power_ctrl() callback error handling

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

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

@@ -455,7 +455,8 @@ int dvb_usbv2_device_power_ctrl(struct dvb_usb_device *d, int onoff)
 		pr_debug("%s: power control=%d\n", __func__, onoff);
 		if (d->props->power_ctrl) {
 			ret = d->props->power_ctrl(d, onoff);
-			goto err;
+			if (ret < 0)
+				goto err;
 		}
 	}