gpio: Kontron PLD gpio driver

Add gpio support for the on-board PLD found on some Kontron embedded modules.

Originally-from: Michael Brunner <michael.brunner@kontron.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>