Open source the missing part of FakeFp16 ops (#36353)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36353
ATT
Test Plan: buck build
Reviewed By: hyuen, amylittleyang
Differential Revision: D20953953
fbshipit-source-id: f6d2562dd3d123f0fcf4c912ed15053bf215d321
