gpio: ks8695: remove irq_to_gpio function

The ks8695 gpio driver has its own copy of the irq_to_gpio()
function. This is completely unused in the mainline kernel
after we converted all remaining users several years ago,
so we can remove the definition as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-ks8695.c

@@ -205,18 +205,6 @@ static int ks8695_gpio_to_irq(struct gpio_chip *gc, unsigned int pin)
 	return gpio_irq[pin];
 }
 
-/*
- * Map IRQ number to GPIO line.
- */
-int irq_to_gpio(unsigned int irq)
-{
-	if ((irq < KS8695_IRQ_EXTERN0) || (irq > KS8695_IRQ_EXTERN3))
-		return -EINVAL;
-
-	return (irq - KS8695_IRQ_EXTERN0);
-}
-EXPORT_SYMBOL(irq_to_gpio);
-
 /* GPIOLIB interface */
 
 static struct gpio_chip ks8695_gpio_chip = {