gpio: max77620: Use irqchip template

gpio: max77620: Use irqchip template

This change addresses one of the GPIO-core TODOs for the MAX77620 driver
which requires modern drivers to use the irqchip template. Instead of
using the GPIO's irqchip-helpers for creating the IRQ domain, the
gpio_irq_chip structure is now filled by the driver itself and then
gpiochip_add_data() takes care of instantiating the IRQ domain for us.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Link: https://lore.kernel.org/r/20200709171203.12950-6-digetx@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>