[Caffe2] Optimize MishOp on CPU (#48212)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48212
Optimize MishOp on CPU
Test Plan: buck test mode/dev-nosan //caffe2/caffe2/python/operator_test:activation_ops_test -- "mish"
Reviewed By: houseroad
Differential Revision: D25071304
fbshipit-source-id: fe94bfab512188d60412d66962983eff4f37bc07
