feat(plat/mediatek/mt8186): add MCDI drivers

Add MCDI related drivers to handle CPU powered on/off in CPU suspend.

TEST=build pass
BUG=b:202871018

Change-Id: I85aaaf3a0e992a39d17c58f3d9d5ff1b5770f748
diff --git a/plat/mediatek/mt8186/drivers/mcdi/mt_mcdi.h b/plat/mediatek/mt8186/drivers/mcdi/mt_mcdi.h
new file mode 100644
index 0000000..0e6444a
--- /dev/null
+++ b/plat/mediatek/mt8186/drivers/mcdi/mt_mcdi.h
@@ -0,0 +1,12 @@
+/*
+ * Copyright (c) 2021, MediaTek Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef MT_MCDI_H
+#define MT_MCDI_H
+
+int mcdi_try_init(void);
+
+#endif /* MT_MCDI_H */