[PyTorch] Don't create a new Storage in FreeMemory unnecessarily
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79573
No reason to go through an extra heap allocation.
Differential Revision: [D37157595](https://our.internmc.facebook.com/intern/diff/D37157595/)
**NOTE FOR REVIEWERS**: This PR has internal Facebook specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D37157595/)!
Approved by: https://github.com/ezyang
