Fix op benchmarks error in OSS environment (#19518)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19518
Previous design needs to run the op benchmarks from PyTorch root directory which could lead to `module not found` error in OSS environment. This diff fixes that issue by making the benchmark to be launched in the `benchmarks` folder.
Reviewed By: ilia-cher
Differential Revision: D15020787
fbshipit-source-id: eb09814a33432a66cc857702bc86538cd17bea3b
