Migrate multinomial from the TH to Aten (CUDA) (#26481)
Summary:
https://github.com/pytorch/pytorch/issues/24604
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26481
Differential Revision: D17489859
Pulled By: ifedan
fbshipit-source-id: 0702044c7c0f78e5e30826e8a5a83da27156bdb3
