Added #ifndef, #define, #endif in DFG2LLVM.h

llvm/include/llvm/SupportVISC/DFG2LLVM.h

+#ifndef __DFG2LLVM_H__
+#define __DFG2LLVM_H__
 
 //===---- DFG2LLVM.h - Header file for "VISC Dataflow Graph to Target" ----===//
 //
@@ -491,3 +493,5 @@ bool hasAttribute(Function* F, unsigned arg_index, Attribute::AttrKind AK) {
 
 } // End of namespace
 
+#endif
+