Revert D28393469: [pytorch][PR] Enable `ceil`, `floor`, `frac`, `round` & `trunc` for BFloat16 on CUDA
Test Plan: revert-hammer
Differential Revision:
D28393469 (https://github.com/pytorch/pytorch/commit/e6d8f45523e2b374653f9cddc9e216aa80c04080)
Original commit changeset: b0f02ade7c6e
fbshipit-source-id: 5e900f240e738168b9db9a617c6a75c949ad36d6
