feat(mt8188): add MT8188 SPM support

Add SPM basic functions including SPM init.

Change-Id: I5d4860685c15f3b8d555e697837862287f0c303e
diff --git a/plat/mediatek/drivers/spm/mt8188/mt_spm_conservation.h b/plat/mediatek/drivers/spm/mt8188/mt_spm_conservation.h
new file mode 100644
index 0000000..4be8567
--- /dev/null
+++ b/plat/mediatek/drivers/spm/mt8188/mt_spm_conservation.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2023, MediaTek Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef MT_SPM_CONSERVATION_H
+#define MT_SPM_CONSERVATION_H
+
+#include "mt_spm_internal.h"
+
+int spm_conservation(int state_id, unsigned int ext_opand,
+		     struct spm_lp_scen *spm_lp,
+		     unsigned int resource_req);
+void spm_conservation_finish(int state_id, unsigned int ext_opand,
+			     struct spm_lp_scen *spm_lp,
+			     struct wake_status **status);
+int spm_conservation_get_result(struct wake_status **res);
+
+#endif /* MT_SPM_CONSERVATION_H */