Strided masked normalize. (#68694)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/68694
Test Plan: Imported from OSS
Reviewed By: samdow
Differential Revision: D32724552
Pulled By: cpuhrsch
fbshipit-source-id: 82f579a86b0b265e0b9b3715a8a327b775dd55e1
