gpio: etraxfs: Fix devm_ioremap_resource return value check

Value returned by devm_ioremap_resource() was checked for non-NULL but
devm_ioremap_resource() returns IOMEM_ERR_PTR, not NULL. In case of
error this could lead to dereference of ERR_PTR.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-etraxfs.c

@@ -117,8 +117,8 @@ static int etraxfs_gpio_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	regs = devm_ioremap_resource(dev, res);
-	if (!regs)
-		return -ENOMEM;
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
 
 	match = of_match_node(etraxfs_gpio_of_table, dev->of_node);
 	if (!match)