gpio: convert remaining users to gpiochip_add_data()

For completion, sweep the floor from all gpiochip_add() usage so
we can remove that function and get rid of the function wrapper
gpiochip_add().

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-iop.c

@@ -114,7 +114,7 @@ static int iop3xx_gpio_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
-	return gpiochip_add(&iop3xx_chip);
+	return gpiochip_add_data(&iop3xx_chip, NULL);
 }
 
 static struct platform_driver iop3xx_gpio_driver = {