feat(mt8196): initialize platform for MediaTek MT8196

- Add basic platform setup.
- Add MT8196 documentation at docs/plat/.
- Add generic CPU helper functions.
- Add basic register address.
- Add timer driver configuration.

Change-Id: I07fcdeb785fcda4a955c11c39a345da4ad05ef04
diff --git a/plat/mediatek/drivers/timer/mt_timer.h b/plat/mediatek/drivers/timer/mt_timer.h
index 1c08f90..fafbbcf 100644
--- a/plat/mediatek/drivers/timer/mt_timer.h
+++ b/plat/mediatek/drivers/timer/mt_timer.h
@@ -7,7 +7,12 @@
 #ifndef MT_TIMER_H
 #define MT_TIMER_H
 
+#include "platform_def.h"
+
+#ifndef SYSTIMER_BASE
 #define SYSTIMER_BASE       (0x10017000)
+#endif
+
 #define CNTCR_REG           (SYSTIMER_BASE + 0x0)
 #define CNTSR_REG           (SYSTIMER_BASE + 0x4)
 #define CNTSYS_L_REG        (SYSTIMER_BASE + 0x8)