Revert D32099294: Split cuda: list cpp files that go in _cu library explicitly
Test Plan: revert-hammer
Differential Revision:
D32099294 (https://github.com/pytorch/pytorch/commit/b47ae9810c1a645f4942737ab4a58b2b1407e7bd)
Original commit changeset: 8a3582944b6b
fbshipit-source-id: eab63e6ba3db3e17f404292a3659823607627576
