fix typo for model.get_flops (#1312)
Summary:
There is a typo when getting flops from fvcore.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1312
Reviewed By: xuzhao9
Differential Revision: D41387779
Pulled By: FindHao
fbshipit-source-id: 9be49c09cae673b52cb75b365fab4647fe5f1f8f
