Delete USE_CUDA macro use from data_parallel.h (#29483)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29483
Somehow, these macros were not necessary!
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D18427851
Pulled By: ezyang
fbshipit-source-id: 86e1d75d98342461c9a5afa1c30c14346188f7cc
