gpiolib: Fix a WARN_ON that can never trigger

"if (!x) WARN_ON(x)" can never trigger.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -1422,7 +1422,6 @@ void devm_gpiochip_remove(struct device *dev, struct gpio_chip *chip)
 
 	ret = devres_release(dev, devm_gpio_chip_release,
 			     devm_gpio_chip_match, chip);
-	if (!ret)
 	WARN_ON(ret);
 }
 EXPORT_SYMBOL_GPL(devm_gpiochip_remove);