can: peak_usb: pcan_usb_get_device_id(): read value only in case of success

In case of error, reading value from response argument is useless.

Link: https://lore.kernel.org/r/20210625130931.27438-2-s.grosjean@peak-system.comSigned-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/peak_usb/pcan_usb.c

@@ -384,7 +384,8 @@ static int pcan_usb_get_device_id(struct peak_usb_device *dev, u32 *device_id)
 	if (err)
 		netdev_err(dev->netdev, "getting device id failure: %d\n", err);
 
-	*device_id = args[0];
+	else
+		*device_id = args[0];
 
 	return err;
 }