[RISCV] Remove unnecessary if guard before calling SignExtend64<6> in decodeCLUIImmOperand. NFC (llvm#133514)

Author: topperc

llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp

@@ -455,8 +455,7 @@ static DecodeStatus decodeCLUIImmOperand(MCInst &Inst, uint32_t Imm,
   assert(isUInt<6>(Imm) && "Invalid immediate");
   if (Imm == 0)
     return MCDisassembler::Fail;
-  if (Imm > 31)
-    Imm = (SignExtend64<6>(Imm) & 0xfffff);
+  Imm = SignExtend64<6>(Imm) & 0xfffff;
   Inst.addOperand(MCOperand::createImm(Imm));
   return MCDisassembler::Success;
 }