Revert "pinctrl: lantiq: Implement gpio_chip.to_irq"

This reverts commit 3e640743fee6e6a82ead1f163737755b2a965712.

This commit needs to go into the pinctrl tree to avoid
clashes.

drivers/pinctrl/pinctrl-xway.c

@@ -682,22 +682,6 @@ static int xway_gpio_dir_out(struct gpio_chip *chip, unsigned int pin, int val)
 	return 0;
 }
 
-/*
- * gpiolib gpiod_to_irq callback function.
- * Returns the mapped IRQ (external interrupt) number for a given GPIO pin.
- */
-static int xway_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
-{
-	struct ltq_pinmux_info *info = dev_get_drvdata(chip->parent);
-	int i;
-
-	for (i = 0; i < info->num_exin; i++)
-		if (info->exin[i] == offset)
-			return ltq_eiu_get_irq(i);
-
-	return -1;
-}
-
 static struct gpio_chip xway_chip = {
 	.label = "gpio-xway",
 	.direction_input = xway_gpio_dir_in,
@@ -706,7 +690,6 @@ static struct gpio_chip xway_chip = {
 	.set = xway_gpio_set,
 	.request = gpiochip_generic_request,
 	.free = gpiochip_generic_free,
-	.to_irq = xway_gpio_to_irq,
 	.base = -1,
 };