gpio/qoriq: select IRQ_DOMAIN

The gpio-mpc8xxx driver requires IRQ domains but can be built
without them, resulting on a failure to build certain randconfigs
on ARM:

drivers/gpio/gpio-mpc8xxx.c: In function 'mpc8xxx_gpio_to_irq':
drivers/gpio/gpio-mpc8xxx.c:92:10: error: implicit declaration of function 'irq_create_mapping' [-Werror=implicit-function-declaration]
   return irq_create_mapping(mpc8xxx_gc->irq, offset);

This selects IRQ_DOMAIN from the driver to ensure we can build it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 5df7fd46 ("gpio/qoriq: Add qoriq platforms support")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>