Make layer_norm dispatch from yaml file to fix XLA test (#28051)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28051
Make layer_norm dispatch from yaml file to fix XLA test
Test Plan: buck test mode/dev-nosan caffe2/test:nn -- "LayerNorm"
Reviewed By: houseroad
Differential Revision: D17939919
fbshipit-source-id: 384b6a8008dabfc1aaeb0357c1bd195be68f1edb
