EmbeddedGpio only supports one gpio controller in one platform. Now create PLATFORM_GPIO_CONTROLLER to support multiple gpio controllers in one platform. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>