feat(mt8188): add audio support

For MT8188, MTK_AUDIO_SMC_OP_DOMAIN_SIDEBANDS is required for normal
mode switch.
  - Add audio common code and chip specific code.
  - Add new id (MTK_SIP_AUDIO_CONTROL) to mtk_sip_def.h.
  - Enable for MT8188.

Change-Id: Iff4680cd0b520b2b519ecf30ecafe100f147cc62
diff --git a/plat/mediatek/mt8188/platform.mk b/plat/mediatek/mt8188/platform.mk
index 92b65e5..b6a17aa 100644
--- a/plat/mediatek/mt8188/platform.mk
+++ b/plat/mediatek/mt8188/platform.mk
@@ -24,6 +24,7 @@
 MODULES-y += $(MTK_PLAT)/lib/mtk_init
 MODULES-y += $(MTK_PLAT)/lib/pm
 MODULES-y += $(MTK_PLAT)/lib/system_reset
+MODULES-y += $(MTK_PLAT)/drivers/audio
 MODULES-y += $(MTK_PLAT)/drivers/cirq
 MODULES-y += $(MTK_PLAT)/drivers/cpu_pm
 MODULES-y += $(MTK_PLAT)/drivers/dcm