PI Enabling: the address of PeiServices Pointer should be

1) Set to preceding of IDT table in PeiCore's entry
2) Migrate to preceding of new memory IDT table when memory is discovery

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4059 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Core/Pei/PeiMain/PeiMain.c

@@ -166,6 +166,11 @@ Returns:
 
   InitializePpiServices (&PrivateData, OldCoreData);
 
+  //
+  // Save PeiServicePointer so that it can be retrieved anywhere.
+  //
+  SetPeiServicesTablePointer(&PrivateData.PS);
+  
   if (OldCoreData != NULL) {
 
     PERF_END (NULL,"PreMem", NULL, 0);