feat(mt8188): add pinctrl support

Add pinctrl support for MT8188.

TEST=build pass
BUG=b:236331724

Signed-off-by: Jianguo Zhang <jianguo.zhang@mediatek.corp-partner.google.com>
Change-Id: Id4ac8f67009621fff8f15f3ab2d8f200343c8356
diff --git a/plat/mediatek/drivers/gpio/mtgpio_common.c b/plat/mediatek/drivers/gpio/mtgpio_common.c
index 90e5400..bad0190 100644
--- a/plat/mediatek/drivers/gpio/mtgpio_common.c
+++ b/plat/mediatek/drivers/gpio/mtgpio_common.c
@@ -9,6 +9,7 @@
 #include <drivers/delay_timer.h>
 #include <drivers/gpio.h>
 #include <lib/mmio.h>
+#include <lib/mtk_init/mtk_init.h>
 #include <mtgpio.h>
 #include <platform_def.h>
 
@@ -292,7 +293,10 @@
 	 .get_pull = mt_get_gpio_pull,
 };
 
-void mt_gpio_init(void)
+int mt_gpio_init(void)
 {
 	gpio_init(&mtgpio_ops);
+
+	return 0;
 }
+MTK_PLAT_SETUP_0_INIT(mt_gpio_init);