serial: imx: restore handshaking irq for imx1

commit 7e620984 upstream.

Back in 2015 when irda was dropped from the driver imx1 was broken. This
change reintroduces the support for the third interrupt of the UART.

Fixes: afe9cbb1 ("serial: imx: drop support for IRDA")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -1997,6 +1997,14 @@ static int serial_imx_probe(struct platform_device *pdev)
 				       dev_name(&pdev->dev), sport);
 		if (ret)
 			return ret;
+
+		ret = devm_request_irq(&pdev->dev, rtsirq, imx_rtsint, 0,
+				       dev_name(&pdev->dev), sport);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to request rts irq: %d\n",
+				ret);
+			return ret;
+		}
 	} else {
 		ret = devm_request_irq(&pdev->dev, rxirq, imx_int, 0,
 				       dev_name(&pdev->dev), sport);