add _to_cpu() operator (#55795)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55795
description coming soon
Test Plan: Imported from OSS
Reviewed By: navahgar
Differential Revision: D28474365
Pulled By: bdhirsh
fbshipit-source-id: 0704d7ce354308601a0af9ab48851459f34ce7a0
