[RISCV][NFC] Use addExpr() instead of createExpr()

[• pcwang-thead]

Summary

It seems to be neater.

[asb]

LGTM, thanks.

llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp

void RISCVMCCodeEmitter::expandFunctionCall(const MCInst &MI, raw_ostream &OS,
   }
   uint32_t Binary;
 
   assert(Func.isExpr() && "Expected expression");
 
   const MCExpr *CallExpr = Func.getExpr();
 
   // Emit AUIPC Ra, Func with R_RISCV_CALL relocation type.
-  TmpInst = MCInstBuilder(RISCV::AUIPC)
-                .addReg(Ra)
-                .addOperand(MCOperand::createExpr(CallExpr));
+  TmpInst = MCInstBuilder(RISCV::AUIPC).addReg(Ra).addExpr(CallExpr);
   Binary = getBinaryCodeForInstr(TmpInst, Fixups, STI);
   support::endian::write(OS, Binary, support::little);
 
   if (MI.getOpcode() == RISCV::PseudoTAIL ||
       MI.getOpcode() == RISCV::PseudoJump)
     // Emit JALR X0, Ra, 0
     TmpInst = MCInstBuilder(RISCV::JALR).addReg(RISCV::X0).addReg(Ra).addImm(0);
   else