Fix the name of a variable to match its declaration. Fixes build failure from r177014.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177015 91177308-0d34-0410-b5e6-96231b3b80d8

Author: topperc

lib/Target/X86/X86CodeEmitter.cpp

@@ -1034,7 +1034,7 @@ void Emitter<CodeEmitter>::emitVEXOpcodePrefix(uint64_t TSFlags,
       if (HasVEX_4V)
         VEX_4V = getVEXRegisterEncoding(MI, CurOp++);
 
-      if (MemOp4) // Skip second register source (encoded in I8IMM)
+      if (HasMemOp4) // Skip second register source (encoded in I8IMM)
         CurOp++;
 
       if (X86II::isX86_64ExtendedReg(MI.getOperand(CurOp).getReg()))