[HLSL][DXIL] Added Intrinsic::dx_wave_prefix_usum to checkWaveOps

Author: kcloudy0717

llvm/lib/Target/DirectX/DXILShaderFlags.cpp

@@ -98,6 +98,7 @@ static bool checkWaveOps(Intrinsic::ID IID) {
   case Intrinsic::dx_wave_reduce_umin:
     // Wave Prefix Op Variants
   case Intrinsic::dx_wave_prefix_sum:
+  case Intrinsic::dx_wave_prefix_usum:
     return true;
   }
 }