HParams for training ASR model on Librispeech on TPU v2.

def transformer_librispeech_tpu_v2():
  """HParams for training ASR model on Librispeech on TPU v2."""
  hparams = transformer_librispeech_v2()
  update_hparams_for_tpu(hparams)

  hparams.batch_size = 16
  librispeech.set_librispeech_length_hparams(hparams)
  return hparams