gpio: xlp: fix error return code

Return a negative error code on failure.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier ret; expression e1,e2;
@@
(
if (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-xlp.c

@@ -387,7 +387,7 @@ static int xlp_gpio_probe(struct platform_device *pdev)
 	irq_base = irq_alloc_descs(-1, XLP_GPIO_IRQ_BASE, gc->ngpio, 0);
 	if (irq_base < 0) {
 		dev_err(&pdev->dev, "Failed to allocate IRQ numbers\n");
-		return err;
+		return -ENODEV;
 	}
 
 	err = gpiochip_add(gc);