Make softmax and log_softmax handle negative dims, add tests (#48156)
Summary:
Make softmax and log_softmax handle negative dims, add tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48156
Reviewed By: bertmaher
Differential Revision: D25059788
Pulled By: Krovatkin
fbshipit-source-id: 985963e7df400857c9774660c76be7d56201a1ad