Make GPIO support optional for platforms that don't support GPIOLIB.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>