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: Sachin Kamat <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-mxc.c

···
 	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);