feat(plat/mdeiatek/mt8192): add DFD control in SiP service

DFD (Design for Debug) is a debugging tool, which scans
flip-flops and dumps to internal RAM on the WDT reset.
After system reboots, those values could be showed for
debugging.

Change-Id: I9c7af9a4f75216ed2c6b44458d121a352bef4b95
diff --git a/plat/mediatek/mt8192/include/plat_sip_calls.h b/plat/mediatek/mt8192/include/plat_sip_calls.h
index 0e42322..f68a4ea 100644
--- a/plat/mediatek/mt8192/include/plat_sip_calls.h
+++ b/plat/mediatek/mt8192/include/plat_sip_calls.h
@@ -10,6 +10,10 @@
 /*******************************************************************************
  * Plat SiP function constants
  ******************************************************************************/
-#define MTK_PLAT_SIP_NUM_CALLS    0
+#define MTK_PLAT_SIP_NUM_CALLS    2
+
+/* DFD */
+#define MTK_SIP_KERNEL_DFD_AARCH32		0x82000205
+#define MTK_SIP_KERNEL_DFD_AARCH64		0xC2000205
 
 #endif /* PLAT_SIP_CALLS_H */