Revert D32498570: make codegen'd device guards not cuda-specific. Allow them to be used in external codegen
Test Plan: revert-hammer
Differential Revision:
D32498570 (https://github.com/pytorch/pytorch/commit/2e7a91c45feb18151b3797ef1e88e5e839749f6d)
Original commit changeset: 0ce6a5614417
Original Phabricator Diff: D32498570 (https://github.com/pytorch/pytorch/commit/2e7a91c45feb18151b3797ef1e88e5e839749f6d)
fbshipit-source-id: 7c64ce1b5e51a680b4aeae8721e0c9e15c793289
