Add explicit cast to cuda_atomic_ops_test.cu (#48886)
Summary:
Should fix linking error reported in https://github.com/pytorch/pytorch/issues/48870
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48886
Reviewed By: walterddr
Differential Revision: D25356601
Pulled By: malfet
fbshipit-source-id: 25282d4606251b27d047917f096868ddb662a723
