serial: RS485 termination is supported if DT provides one

When DT provides rs485-term, set termination flag as supported.
Reviewed-by: NLino Sanfilippo <l.sanfilippo@kunbus.com>
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220704094515.6831-3-ilpo.jarvinen@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_core.c

@@ -3409,6 +3409,8 @@ int uart_get_rs485_mode(struct uart_port *port)
 		port->rs485_term_gpio = NULL;
 		return dev_err_probe(dev, ret, "Cannot get rs485-term-gpios\n");
 	}
+	if (port->rs485_term_gpio)
+		port->rs485_supported.flags |= SER_RS485_TERMINATE_BUS;
 
 	return 0;
 }