serial: imx: Use common rs485 device tree parsing function

This adds support for the rs485 specific properties defined in
Documentation/devicetree/bindings/serial/rs485.txt.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Forwarded: id:20170913081833.2740-7-u.kleine-koenig@pengutronix.de (v5)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -2051,6 +2051,8 @@ static int serial_imx_probe_dt(struct imx_port *sport,
 	if (of_get_property(np, "rts-gpios", NULL))
 		sport->have_rtsgpio = 1;
 
+	of_get_rs485_mode(np, &sport->port.rs485);
+
 	return 0;
 }
 #else
@@ -2112,7 +2114,7 @@ static int serial_imx_probe(struct platform_device *pdev)
 	sport->port.fifosize = 32;
 	sport->port.ops = &imx_pops;
 	sport->port.rs485_config = imx_rs485_config;
-	sport->port.rs485.flags = SER_RS485_RTS_ON_SEND;
+	sport->port.rs485.flags |= SER_RS485_RTS_ON_SEND;
 	sport->port.flags = UPF_BOOT_AUTOCONF;
 	init_timer(&sport->timer);
 	sport->timer.function = imx_timeout;