feat(plat/mediatek/mt8186): initialize GIC

Initialize GIC for mt8186.

TEST=build pass
BUG=b:202871018

Signed-off-by: Christine Zhu <christine.zhu@mediatek.corp-partner.google.com>
Change-Id: I8d029983c7ce48fa116fafa7fa78c65349308014
diff --git a/plat/mediatek/mt8186/include/platform_def.h b/plat/mediatek/mt8186/include/platform_def.h
index 27cd4da..72fc0a6 100644
--- a/plat/mediatek/mt8186/include/platform_def.h
+++ b/plat/mediatek/mt8186/include/platform_def.h
@@ -40,6 +40,13 @@
 #define EMI_MPU_BASE		(IO_PHYS + 0x0021B000)
 
 /*******************************************************************************
+ * 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_TICKS	13000000