gpio: aspeed: fix return value check in aspeed_gpio_probe()

In case of error, the function devm_ioremap_resource() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR().

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-aspeed.c

@@ -413,8 +413,8 @@ static int __init aspeed_gpio_probe(struct platform_device *pdev)
 		return -ENXIO;
 
 	gpio->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!gpio->base)
-		return -ENOMEM;
+	if (IS_ERR(gpio->base))
+		return PTR_ERR(gpio->base);
 
 	spin_lock_init(&gpio->lock);