GlobalISel: Correct result type for G_FCMP in lowerFPTOUI

Using the final result type doesn't make any sense. Use the natural
default boolean type for the select condition.
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 52c43f0..bb3ece3 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -3996,8 +3996,10 @@
   MachineInstrBuilder ResHighBit = MIRBuilder.buildConstant(DstTy, TwoPExpInt);
   MachineInstrBuilder Res = MIRBuilder.buildXor(DstTy, ResLowBits, ResHighBit);
 
+  const LLT S1 = LLT::scalar(1);
+
   MachineInstrBuilder FCMP =
-      MIRBuilder.buildFCmp(CmpInst::FCMP_ULT, DstTy, Src, Threshold);
+      MIRBuilder.buildFCmp(CmpInst::FCMP_ULT, S1, Src, Threshold);
   MIRBuilder.buildSelect(Dst, FCMP, FPTOSI, Res);
 
   MI.eraseFromParent();