Remove git lfs and add readme on Amazon S3 data host (#1468)
Summary:
Fixes https://github.com/pytorch/benchmark/issues/1464
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1468
Reviewed By: janeyx99
Differential Revision: D43914775
Pulled By: xuzhao9
fbshipit-source-id: d247141680a1d4855e355a53777037e42228574c
