gpio: ep93xx: drop to_irq binding

As ->to_irq is redefined in gpiochip_add_irqchip, having it defined in
driver is useless, so let's drop it.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpio-ep93xx.c

@@ -318,11 +318,6 @@ static int ep93xx_gpio_set_config(struct gpio_chip *gc, unsigned offset,
 	return 0;
 }
 
-static int ep93xx_gpio_f_to_irq(struct gpio_chip *gc, unsigned offset)
-{
-	return EP93XX_GPIO_F_IRQ_BASE + offset;
-}
-
 static void ep93xx_init_irq_chip(struct device *dev, struct irq_chip *ic)
 {
 	ic->irq_ack = ep93xx_gpio_irq_ack;
@@ -415,7 +410,6 @@ static int ep93xx_gpio_add_bank(struct ep93xx_gpio_chip *egc,
 		}
 		girq->default_type = IRQ_TYPE_NONE;
 		girq->handler = handle_level_irq;
-		gc->to_irq = ep93xx_gpio_f_to_irq;
 		girq->first = EP93XX_GPIO_F_IRQ_BASE;
 	}