AMDGPU/GlobalISel: Don't pointlessly check for convergent intrinsics

The set of handled intrinsics for fneg combines aren't convergent. The only
case we might want to handle is mov_dpp.

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp

@@ -42,8 +42,7 @@ static bool fnegFoldsIntoMI(const MachineInstr &MI) {
   case AMDGPU::G_AMDGPU_FMIN_LEGACY:
   case AMDGPU::G_AMDGPU_FMAX_LEGACY:
     return true;
-  case AMDGPU::G_INTRINSIC:
-  case AMDGPU::G_INTRINSIC_CONVERGENT: {
+  case AMDGPU::G_INTRINSIC: {
     unsigned IntrinsicID = cast<GIntrinsic>(MI).getIntrinsicID();
     switch (IntrinsicID) {
     case Intrinsic::amdgcn_rcp: