pinctrl: ingenic: Factorize irq_set_type function

Simplify the code of the driver's irq_set_type() function by doing some
factorization. The behaviour is unchanged.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200106232711.559727-5-paul@crapouillou.net


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>