Make data_ptr a method on Tensor (#20878)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20878
ghimport-source-id: f19993d97ecb8cfcd60b371d9ed49e3ad2e051c7
Differential Revision: D15482061
Pulled By: li-roy
fbshipit-source-id: c0563ce849fc3277e86a1a58bd384e38365786b2
