Revert "Add CC_Win64ThisCall and set it in the necessary places."

This reverts commit 126863.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126886 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenTypes.h b/lib/CodeGen/CodeGenTypes.h
index 6bf3f92..41513da 100644
--- a/lib/CodeGen/CodeGenTypes.h
+++ b/lib/CodeGen/CodeGenTypes.h
@@ -161,11 +161,9 @@
                                         CXXDtorType Type);
 
   const CGFunctionInfo &getFunctionInfo(const CallArgList &Args,
-                                        const FunctionType *Ty,
-                                        CallingConv CC) {
-    FunctionType::ExtInfo Info = Ty->getExtInfo().withCallingConv(CC);
-
-    return getFunctionInfo(Ty->getResultType(), Args, Info);
+                                        const FunctionType *Ty) {
+    return getFunctionInfo(Ty->getResultType(), Args,
+                           Ty->getExtInfo());
   }
 
   const CGFunctionInfo &getFunctionInfo(CanQual<FunctionProtoType> Ty,