[llvm] Remove redundant return [NFC]

[Eugene.Zelenko]

It make sense to run other Clang-tidy modernize/misc/readability checks at same time.

lib/IR/Instruction.cpp

void Instruction::copyMetadata(const Instruction &SrcInst,
   SmallVector<std::pair<unsigned, MDNode *>, 4> TheMDs;
   SrcInst.getAllMetadataOtherThanDebugLoc(TheMDs);
   for (const auto &MD : TheMDs) {
     if (WL.empty() || WLS.count(MD.first))
       setMetadata(MD.first, MD.second);
   }
   if (WL.empty() || WLS.count(LLVMContext::MD_dbg))
     setDebugLoc(SrcInst.getDebugLoc());
-  return;
 }
 
 Instruction *Instruction::clone() const {
   Instruction *New = nullptr;
   switch (getOpcode()) {
   default:
     llvm_unreachable("Unhandled Opcode.");
 #define HANDLE_INST(num, opc, clas)                                            \

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

void ARMAsmParser::fixupGNULDRDAlias(StringRef Mnemonic,
   unsigned PairedReg = GPR.getRegister(RtEncoding + 1);
   if (!PairedReg || PairedReg == ARM::PC ||
       (PairedReg == ARM::SP && !hasV8Ops()))
     return;
 
   Operands.insert(
       Operands.begin() + 3,
       ARMOperand::CreateReg(PairedReg, Op2.getStartLoc(), Op2.getEndLoc()));
-  return;
 }
 
 /// Parse an arm instruction mnemonic followed by its operands.
 bool ARMAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
                                     SMLoc NameLoc, OperandVector &Operands) {
   MCAsmParser &Parser = getParser();
   // FIXME: Can this be done via tablegen in some fashion?
   bool RequireVFPRegisterListCheck;

lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp

 
 void MipsInstPrinter::
 printMemOperandEA(const MCInst *MI, int opNum, raw_ostream &O) {
   // when using stack locations for not load/store instructions
   // print the same way as all normal 3 operand instructions.
   printOperand(MI, opNum, O);
   O << ", ";
   printOperand(MI, opNum+1, O);
-  return;
 }
 
 void MipsInstPrinter::
 printFCCOperand(const MCInst *MI, int opNum, raw_ostream &O) {
   const MCOperand& MO = MI->getOperand(opNum);
   O << MipsFCCToString((Mips::CondCode)MO.getImm());
 }