gpio: Add support for IDT 79RC3243x GPIO controller

IDT 79RC3243x SoCs integrated a gpio controller, which handles up
to 32 gpios. All gpios could be used as an interrupt source.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>