Migrate erfc from TH to ATen (CUDA) (#38373)
Summary:
Fixed https://github.com/pytorch/pytorch/issues/24559
Reference https://github.com/pytorch/pytorch/issues/24507
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38373
Differential Revision: D21549626
Pulled By: ezyang
fbshipit-source-id: 84c2cf58b071df3afc312ae0aef3b5ed6c014cc7