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(). The irqchip is
instead added while adding the gpiochip.

Cc: Eudean Sun <eudean@arista.com>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>