pinctrl: ssbi-gpio: convert to hierarchical IRQ helpers in gpio core

Now that the GPIO core has support for hierarchical IRQ chips, convert
Qualcomm's ssbi-gpio over to use these new helpers to reduce duplicated
code across drivers.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Link: https://lore.kernel.org/r/20190914111010.24384-1-masneyb@onstation.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>