Removed unwanted helper function hasXnackReplay.

Author: cdevadas

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -1012,7 +1012,6 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
 
   bool hasLDSFPAtomicAddF32() const { return GFX8Insts; }
   bool hasLDSFPAtomicAddF64() const { return GFX90AInsts; }
-  bool hasXnackReplay() const { return GFX8Insts; }
 
   /// \returns true if the subtarget has the v_permlanex16_b32 instruction.
   bool hasPermLaneX16() const { return getGeneration() >= GFX10; }