Use cos_sim for amp precision in correctness checks (#1336)
Summary:
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1336
cosine similarity doesn't check dtyp, so this makes correctness checks pass. Tested on hf_T5 and resnet50 with:
```
$ python run.py [model] -t train -d cuda --precision amp --torchdynamo inductor
```
Test Plan: Imported from OSS
Reviewed By: xuzhao9
Differential Revision: D41788114
Pulled By: davidberard98
fbshipit-source-id: f5484e9356a41103f77cab204f307ad175d31525
