batch size 0 support in norm operators (#26894)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26894
Add batch_size == 0 testings of norm DNNLOWP operators.
Test Plan: CI
Reviewed By: jianyuh
Differential Revision: D17595416
fbshipit-source-id: 23086ecf8818be30da031eb4fc2922daea79ea7c
