Migrate some CUDA arithmetic kernels to c10::complex (#37878)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/37878
Test Plan: Imported from OSS
Differential Revision: D21426621
Pulled By: anjali411
fbshipit-source-id: 6cdf0ee7320e5c4c2864331b1eaff4201d74ccf7
