[MC] Remove dead code, NFC

[pengfei]

Summary

This code was added in 408b5e660300f9, but neither the return value nor
Res was used in the following code.

[pengfei]

Sorry, this was commited in accident. But I don't want to rush for reverting since it is a NFC patch. Let me know if you have concerns or revert it directly please.

llvm/lib/MC/MCCodeView.cpp

 //===- MCCodeView.h - Machine Code CodeView support -------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
for (size_t I = 0, E = Frag.getRanges().size(); I != E;) {
     // We must split the range into chunks of MaxDefRange, this is a fundamental
     // limitation of the file format.
     do {
       uint16_t Chunk = std::min((uint32_t)MaxDefRange, RangeSize);
 
       const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(RangeBegin, Ctx);
       const MCBinaryExpr *BE =
           MCBinaryExpr::createAdd(SRE, MCConstantExpr::create(Bias, Ctx), Ctx);
-      MCValue Res;
-      BE->evaluateAsRelocatable(Res, &Layout, /*Fixup=*/nullptr);
 
       // Each record begins with a 2-byte number indicating how large the record
       // is.
       StringRef FixedSizePortion = Frag.getFixedSizePortion();
       // Our record is a fixed sized prefix and a LocalVariableAddrRange that we
       // are artificially constructing.
       size_t RecordSize = FixedSizePortion.size() +
                           sizeof(LocalVariableAddrRange) + 4 * NumGaps;