feat(mt8188): initialize GIC

Initialize GIC for mt8188.

TEST=build pass
BUG=b:236331724

Change-Id: I5acf77d654f1bbce32e9fbb3f3567600b7db10ed
diff --git a/plat/mediatek/include/mt8188/platform_def.h b/plat/mediatek/include/mt8188/platform_def.h
index 946ac04..c09139c 100644
--- a/plat/mediatek/include/mt8188/platform_def.h
+++ b/plat/mediatek/include/mt8188/platform_def.h
@@ -26,6 +26,13 @@
 #define UART_BAUDRATE	(115200)
 
 /*******************************************************************************
+ * GIC-600 & interrupt handling related constants
+ ******************************************************************************/
+/* Base MTK_platform compatible GIC memory map */
+#define BASE_GICD_BASE		(MT_GIC_BASE)
+#define MT_GIC_RDIST_BASE	(MT_GIC_BASE + 0x40000)
+
+/*******************************************************************************
  * System counter frequency related constants
  ******************************************************************************/
 #define SYS_COUNTER_FREQ_IN_HZ	(13000000)