Move scalar_check logic from codegen to code in NLLLoss. (#30670)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30670
Also turn off scalar_check for grad_input: it isn't necessary because the input can't be 0-dimensional.
Test Plan: Imported from OSS
Differential Revision: D18784523
Pulled By: gchanan
fbshipit-source-id: 246d30970457075a0403dd0089317659a2cd2dd4
