Lowering NLLLoss/CrossEntropyLoss to ATen code (#53789)
Summary:
* Lowering NLLLoss/CrossEntropyLoss to ATen dispatch
* This allows the MLC device to override these ops
* Reduce code duplication between the Python and C++ APIs.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53789
Reviewed By: ailzhang
Differential Revision: D27345793
Pulled By: albanD
fbshipit-source-id: 99c0d617ed5e7ee8f27f7a495a25ab4158d9aad6
