AMDGPU: Fix gcc -Wenum-compare warning (llvm#138529)

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

@@ -2971,7 +2971,8 @@ SDValue AMDGPUTargetLowering::lowerFEXP10Unsafe(SDValue X, const SDLoc &SL,
                                                 SelectionDAG &DAG,
                                                 SDNodeFlags Flags) const {
   const EVT VT = X.getValueType();
-  const unsigned Exp2Op = VT == MVT::f32 ? AMDGPUISD::EXP : ISD::FEXP2;
+  const unsigned Exp2Op = VT == MVT::f32 ? static_cast<unsigned>(AMDGPUISD::EXP)
+                                         : static_cast<unsigned>(ISD::FEXP2);
 
   if (VT != MVT::f32 || !needsDenormHandlingF32(DAG, X, Flags)) {
     // exp2(x * 0x1.a92000p+1f) * exp2(x * 0x1.4f0978p-11f);