can: kvaser_usb: fix return value for hif_usb_send_regout

As the potential failure of usb_submit_urb(), it should be better to
return the err variable to catch the error.
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Link: https://lore.kernel.org/all/20240521041020.1519416-1-nichen@iscas.ac.cnSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c

@@ -294,7 +294,7 @@ int kvaser_usb_send_cmd_async(struct kvaser_usb_net_priv *priv, void *cmd,
 	}
 	usb_free_urb(urb);
 
-	return 0;
+	return err;
 }
 
 int kvaser_usb_can_rx_over_error(struct net_device *netdev)