feat(mt8186): add SPM suspend driver

Add SPM suspend driver for suspend/resume features.

TEST=build pass
BUG=b:202871018

Change-Id: I25b4b97cd3138a7b347385539e47ccfa884d64fc
diff --git a/plat/mediatek/mt8186/include/plat_mtk_lpm.h b/plat/mediatek/mt8186/include/plat_mtk_lpm.h
index 347f358..12ea9d7 100644
--- a/plat/mediatek/mt8186/include/plat_mtk_lpm.h
+++ b/plat/mediatek/mt8186/include/plat_mtk_lpm.h
@@ -44,5 +44,6 @@
 };
 
 const struct mt_lpm_tz *mt_plat_cpu_pm_init(void);
+int plat_mt_pm_register(struct mt_lpm_tz *mt_pm);
 
 #endif /* PLAT_MTK_LPM_H */