Mark unused functions with `C10_UNUSED` (#62929)
Summary:
Which fixes number of warnings
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62929
Reviewed By: walterddr, albanD
Differential Revision: D30171953
Pulled By: malfet
fbshipit-source-id: f82475289ff4aebb0c97794114e94a24d00d2ff4
