DAG: Change round-mode operand type to i32 for FPTRUNC_ROUND (llvm#106424)

We need this immediate type to be consistent. This is the pre-commit for
llvm#105761

Author: changpeng

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -6957,8 +6957,7 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
     SDValue Result;
     Result = DAG.getNode(
         ISD::FPTRUNC_ROUND, sdl, VT, getValue(I.getArgOperand(0)),
-        DAG.getTargetConstant((int)*RoundMode, sdl,
-                              TLI.getPointerTy(DAG.getDataLayout())));
+        DAG.getTargetConstant((int)*RoundMode, sdl, MVT::i32));
     setValue(&I, Result);
 
     return;