feat(mt8188): add MCUSYS support

Add MCUSYS drivers support for MT8188.

Change-Id: I84107702a9fd021c37d2997ad25b321a483a1a66
diff --git a/plat/mediatek/drivers/mcusys/mcusys.c b/plat/mediatek/drivers/mcusys/mcusys.c
new file mode 100644
index 0000000..63edb23
--- /dev/null
+++ b/plat/mediatek/drivers/mcusys/mcusys.c
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2022, MediaTek Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdint.h>
+#include <mtk_mmap_pool.h>
+#include <platform_def.h>
+
+static const mmap_region_t mcusys_mmap[] MTK_MMAP_SECTION = {
+	MAP_REGION_FLAT(MCUCFG_BASE, MCUCFG_REG_SIZE, MT_DEVICE | MT_RW | MT_SECURE),
+	{0}
+};
+DECLARE_MTK_MMAP_REGIONS(mcusys_mmap);