feat(mt8188): add SPM feature support

Add SPM low power functions, such as system suspend.

Change-Id: I6d1ad847a81ba9c347ab6fb8a8cb8c69004b7add
diff --git a/plat/mediatek/drivers/spm/mt8188/rules.mk b/plat/mediatek/drivers/spm/mt8188/rules.mk
index 7516bc2..a04e91f 100644
--- a/plat/mediatek/drivers/spm/mt8188/rules.mk
+++ b/plat/mediatek/drivers/spm/mt8188/rules.mk
@@ -12,7 +12,7 @@
 endef
 UPPER_DIR := $(call GET_UPPER_DIR)
 
-MT_SPM_FEATURE_SUPPORT := n
+MT_SPM_FEATURE_SUPPORT := y
 MT_SPM_CIRQ_FEATURE_SUPPORT := n
 MT_SPMFW_SPM_SRAM_SLEEP_SUPPORT := n
 MT_SPM_SSPM_NOTIFIER_SUPPORT := y