Generalise BERT_pytorch's device option (#1801)
Summary:
Generalises the interface to the `BERT_pytorch` model so that you can use arbitrary devices, not just CPU or CUDA.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1801
Reviewed By: FindHao
Differential Revision: D47954195
Pulled By: xuzhao9
fbshipit-source-id: 51092614052a57c1c22e29b697a9aef2a8aa285b
