gpio: pxa: Fix potential NULL dereference

platform_get_resource() may fail and return NULL, so we should
better check it's return value to avoid a NULL pointer dereference
a bit later in the code.

This is detected by Coccinelle semantic patch.

@@
expression pdev, res, n, t, e, e1, e2;
@@

res = platform_get_resource(pdev, t, n);
+ if (!res)
+   return -EINVAL;
... when != res == NULL
e = devm_ioremap(e1, res->start, e2);

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pxa.c

@@ -646,6 +646,8 @@ static int pxa_gpio_probe(struct platform_device *pdev)
 	pchip->irq0 = irq0;
 	pchip->irq1 = irq1;
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
 	gpio_reg_base = devm_ioremap(&pdev->dev, res->start,
 				     resource_size(res));
 	if (!gpio_reg_base)