gpio: fix gpio-adp5588 build errors

The gpio-adp5588 driver uses interfaces that are provided by
GPIOLIB_IRQCHIP, so select that symbol in its Kconfig entry.

Fixes these build errors:

../drivers/gpio/gpio-adp5588.c: In function ‘adp5588_irq_handler’:
../drivers/gpio/gpio-adp5588.c:266:26: error: ‘struct gpio_chip’ has no member named ‘irq’
            dev->gpio_chip.irq.domain, gpio));
                          ^
../drivers/gpio/gpio-adp5588.c: In function ‘adp5588_irq_setup’:
../drivers/gpio/gpio-adp5588.c:298:2: error: implicit declaration of function ‘gpiochip_irqchip_add_nested’ [-Werror=implicit-function-declaration]
  ret = gpiochip_irqchip_add_nested(&dev->gpio_chip,
  ^
../drivers/gpio/gpio-adp5588.c:307:2: error: implicit declaration of function ‘gpiochip_set_nested_irqchip’ [-Werror=implicit-function-declaration]
  gpiochip_set_nested_irqchip(&dev->gpio_chip,
  ^

Fixes: 459773ae ("gpio: adp5588-gpio: support interrupt controller")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-gpio@vger.kernel.org
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>