serial: imx: restore handshaking irq for imx1

BugLink: https://bugs.launchpad.net/bugs/1798770

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>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

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);