feat(mt8188): add secure iommu support

The secure IOMMU has two secure banks: VDO and VPP. Add SiP call to
report the secure bank status in debug build.
About more background, please see:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/dt-bindings/memory/mediatek,mt8188-memory-port.h?id=d5cda142d649c690fb0fcf1e29f3df63fbafc442

Change-Id: I7b3319e84391fc6d7f456659f8b8c5d9d1c6ab9d
Signed-off-by: Anan Sun <anan.sun@mediatek.corp-partner.google.com>
Signed-off-by: Kiwi Liu <kiwi.liu@mediatek.corp-partner.google.com>
diff --git a/plat/mediatek/drivers/iommu/mtk_iommu_smc.h b/plat/mediatek/drivers/iommu/mtk_iommu_smc.h
new file mode 100644
index 0000000..9537dbe
--- /dev/null
+++ b/plat/mediatek/drivers/iommu/mtk_iommu_smc.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2023, MediaTek Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef IOMMU_SMC_H
+#define IOMMU_SMC_H
+
+#include <mtk_sip_svc.h>
+
+u_register_t mtk_iommu_handler(u_register_t x1, u_register_t x2,
+			u_register_t x3, u_register_t x4,
+			void *handle, struct smccc_res *smccc_ret);
+#endif