add BFloat16 support for MaxPool2d on CPU (#56903)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56903
Test Plan: Imported from OSS
Reviewed By: mikaylagawarecki
Differential Revision: D28836791
Pulled By: VitalyFedyunin
fbshipit-source-id: e03d55cc30dfa3628f096938fbad34b1031948af
