serial: imx: fix a possible NULL dereference

of_match_device could return NULL, and so cause a NULL pointer
dereference later.
Even if the probability of this case is very low, fixing it made
static analyzers happy.
Solving this with of_device_get_match_data made also code simplier.
Signed-off-by: NLABBE Corentin <clabbe.montjoie@gmail.com>
Acked-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -1857,11 +1857,10 @@ static int serial_imx_probe_dt(struct imx_port *sport,
 		struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
-	const struct of_device_id *of_id =
-			of_match_device(imx_uart_dt_ids, &pdev->dev);
 	int ret;
 
-	if (!np)
+	sport->devdata = of_device_get_match_data(&pdev->dev);
+	if (!sport->devdata)
 		/* no device tree device */
 		return 1;
 
@@ -1878,8 +1877,6 @@ static int serial_imx_probe_dt(struct imx_port *sport,
 	if (of_get_property(np, "fsl,dte-mode", NULL))
 		sport->dte_mode = 1;
 
-	sport->devdata = of_id->data;
-
 	return 0;
 }
 #else