gpiolib: Fix GPIO chip IRQ initialization restriction

In case of gpio-regmap, IRQ chip is added by regmap-irq and associated with
GPIO chip by gpiochip_irqchip_add_domain(). The initialization flag was not
added in gpiochip_irqchip_add_domain(), causing gpiochip_to_irq() to return
-EPROBE_DEFER.

Fixes: 5467801f ("gpio: Restrict usage of GPIO chip irq members before initialization")
Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>