serial: xilinx: Use platform_get_irq to get irq description structure

For systems with CONFIG_SERIAL_OF_PLATFORM=y and device_type =
"serial"; property in DT of_serial.c driver maps and unmaps IRQ (because
driver probe fails). Then a driver is called but irq mapping is not
created that's why driver is failing again in again on request_irq().
Based on this use platform_get_irq() instead of platform_get_resource()
which is doing irq_desc allocation and driver itself can request IRQ.

Fix both xilinx serial drivers in the tree.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c
index 708eead..b1c6bd3 100644
--- a/drivers/tty/serial/uartlite.c
+++ b/drivers/tty/serial/uartlite.c
@@ -632,7 +632,8 @@
 
 static int ulite_probe(struct platform_device *pdev)
 {
-	struct resource *res, *res2;
+	struct resource *res;
+	int irq;
 	int id = pdev->id;
 #ifdef CONFIG_OF
 	const __be32 *prop;
@@ -646,11 +647,11 @@
 	if (!res)
 		return -ENODEV;
 
-	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
-	if (!res2)
-		return -ENODEV;
+	irq = platform_get_irq(pdev, 0);
+	if (irq <= 0)
+		return -ENXIO;
 
-	return ulite_assign(&pdev->dev, id, res->start, res2->start);
+	return ulite_assign(&pdev->dev, id, res->start, irq);
 }
 
 static int ulite_remove(struct platform_device *pdev)