gpio: mxc: Do not hard code return value

Silences the following warning:
why not propagate 'port->irq' from platform_get_irq() instead of (-22)?
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mxc.c

@@ -422,7 +422,7 @@ static int mxc_gpio_probe(struct platform_device *pdev)
 	port->irq_high = platform_get_irq(pdev, 1);
 	port->irq = platform_get_irq(pdev, 0);
 	if (port->irq < 0)
-		return -EINVAL;
+		return port->irq;
 
 	/* disable the interrupt and clear the status */
 	writel(0, port->base + GPIO_IMR);