gpio: dwapb: Discard GPIO-to-IRQ mapping function

Since GPIOlib-based IRQ-chip interface is now utilized there is no need in
setting up a custom GPIO-to-IRQ mapping method. GPIO-lib defines the
standard mapping method - gpiochip_to_irq(), which will be used anyway no
matter whether the custom to_irq callback is specified or not.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200730152808.2955-7-Sergey.Semin@baikalelectronics.ruSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-dwapb.c

@@ -154,14 +154,6 @@ static inline void dwapb_write(struct dwapb_gpio *gpio, unsigned int offset,
 	gc->write_reg(reg_base + gpio_reg_convert(gpio, offset), val);
 }
 
-static int dwapb_gpio_to_irq(struct gpio_chip *gc, unsigned offset)
-{
-	struct dwapb_gpio_port *port = gpiochip_get_data(gc);
-	struct dwapb_gpio *gpio = port->gpio;
-
-	return irq_find_mapping(gpio->domain, offset);
-}
-
 static struct dwapb_gpio_port *dwapb_offs_to_port(struct dwapb_gpio *gpio, unsigned int offs)
 {
 	struct dwapb_gpio_port *port;
@@ -476,8 +468,6 @@ static void dwapb_configure_irqs(struct dwapb_gpio *gpio,
 
 	girq->chip = &pirq->irqchip;
 
-	port->gc.to_irq = dwapb_gpio_to_irq;
-
 	return;
 
 err_kfree_pirq: