gpio: aspeed: fix a potential NULL pointer dereference

In case devm_kzalloc, the patch returns ENOMEM to avoid potential
NULL pointer dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpio-aspeed.c

@@ -1224,6 +1224,8 @@ static int __init aspeed_gpio_probe(struct platform_device *pdev)
 
 	gpio->offset_timer =
 		devm_kzalloc(&pdev->dev, gpio->chip.ngpio, GFP_KERNEL);
+	if (!gpio->offset_timer)
+		return -ENOMEM;
 
 	return aspeed_gpio_setup_irqs(gpio, pdev);
 }