message: Remove redundant kernel registrations
  Summary:
  These are no longer required now that TF/XLA supports looping through
  XlaWhile and xla.compile clustering.
  Fixes: T7755
  Test Plan: All tests ok.
  Reviewers: #tensorflow, georgep
diff: @@ -111,20 +111,4 @@ REGISTER_XLA_RUN_KERNEL(DEVICE_XLA_IPU, XlaRunOp, GetIPUSupportedTypes());
  REGISTER_XLA_DEVICE_KERNELS(DEVICE_XLA_IPU, GetIPUSupportedTypes());
  -// Additional ops not explicitly defined by standard JIT
  -
  -REGISTER_KERNEL_BUILDER(Name("RefEnter").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("RefExit").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("RefMerge").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("RefNextIteration").Device(DEVICE_IPU_XLA_JIT),
  - NoOp);
  -REGISTER_KERNEL_BUILDER(Name("RefSwitch").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -
  -REGISTER_KERNEL_BUILDER(Name("Enter").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("Exit").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("LoopCond").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("Merge").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("NextIteration").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -REGISTER_KERNEL_BUILDER(Name("Switch").Device(DEVICE_IPU_XLA_JIT), NoOp);
  -
  } // namespace tensorflow
  