gpiolib: rework quirk handling in of_find_gpio()

Instead of having a string of "if" statements let's put all quirks into
an array and iterate over them.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>