expose memory_fraction and gpu_process docs (#51372)
Summary:
Per title
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51372
Reviewed By: mruberry
Differential Revision: D26157787
Pulled By: ngimel
fbshipit-source-id: 97eac5f12881a2bf62c251f6f7eaf65fdbe34056
