pinctrl: sx150x: Use irqchip template

This makes the driver use the irqchip template to assign
properties to the gpio_irq_chip instead of using the
explicit calls to gpiochip_irqchip_add_nested() and
gpiochip_set_nested_irqchip(). The irqchip is instead
added while adding the gpiochip.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Cc: Peter Rosin <peda@axentia.se>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20200721132537.362160-1-linus.walleij@linaro.org