C++ API: torch::nn::Softmin (#27459)
Summary:
Add torch::nn::Softmin module and functional support for the C++ API.
Related Issue: https://github.com/pytorch/pytorch/issues/25883
Reviewer: yf225
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27459
Differential Revision: D17892852
Pulled By: yf225
fbshipit-source-id: db15b06e8ad33947e7d65995df700f5e90c3b6a8
