optimize max pool 2d (#17391)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17391
Optimize 2D max pool using AVX2 intrinsics.
Reviewed By: jianyuh
Differential Revision: D14181620
fbshipit-source-id: ffc6c4412bd1c1d7839fe06226921df40d9cab83
