gpio: xgene: Prevent NULL pointer dereference

platform_get_resource() can return NULL, thus add NULL test to prevent NULL
pointer dereference.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-xgene.c

@@ -173,6 +173,11 @@ static int xgene_gpio_probe(struct platform_device *pdev)
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		err = -EINVAL;
+		goto err;
+	}
+
 	gpio->base = devm_ioremap_nocache(&pdev->dev, res->start,
 							resource_size(res));
 	if (!gpio->base) {