gpio: gpio-altera: Remove gpiochip on probe failure.

On failure to setup the irq altera_gpio_probe would return an error
but not go to cleanup. This resulted in kernel fault
"Unable to handle kernel paging request at virtual address xxxxxxxx"
later on in of_gpiochip_find_and_xlate.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-altera.c

@@ -312,8 +312,8 @@ static int altera_gpio_probe(struct platform_device *pdev)
 		handle_simple_irq, IRQ_TYPE_NONE);
 
 	if (ret) {
-		dev_info(&pdev->dev, "could not add irqchip\n");
-		return ret;
+		dev_err(&pdev->dev, "could not add irqchip\n");
+		goto teardown;
 	}
 
 	gpiochip_set_chained_irqchip(&altera_gc->mmchip.gc,
@@ -326,6 +326,7 @@ static int altera_gpio_probe(struct platform_device *pdev)
 skip_irq:
 	return 0;
 teardown:
+	of_mm_gpiochip_remove(&altera_gc->mmchip);
 	pr_err("%s: registration failed with status %d\n",
 		node->full_name, ret);