BFloat16: enable prepacked weights's inference (#48922)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/48922
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D25537188
Pulled By: VitalyFedyunin
fbshipit-source-id: ab6eb1ba8cffb5ba9d00d05db8ef616628f8c932
