feat(mt8188): add display port control in SiP service

MTK display port mute/unmute control registers need to be
set in secure world.

TEST=build pass
BUG=b:236331724

Change-Id: I0aa0675f07c80aab4349493bfbb0782bf0bbef58
diff --git a/plat/mediatek/include/mtk_sip_def.h b/plat/mediatek/include/mtk_sip_def.h
index b591499..37734ea 100644
--- a/plat/mediatek/include/mtk_sip_def.h
+++ b/plat/mediatek/include/mtk_sip_def.h
@@ -12,6 +12,7 @@
 	_func(MTK_SIP_KERNEL_TIME_SYNC, 0x202) \
 	_func(MTK_SIP_VCORE_CONTROL, 0x506) \
 	_func(MTK_SIP_APUSYS_CONTROL, 0x51E) \
+	_func(MTK_SIP_DP_CONTROL, 0x523) \
 	_func(MTK_SIP_KERNEL_GIC_OP, 0x526)
 
 #define MTK_SIP_SMC_FROM_BL33_TABLE(_func) \