[nnc] Added a check to vectorize only those loops that are normalized. (#59423)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/59423
Test Plan: Imported from OSS
Reviewed By: huiguoo
Differential Revision: D28886979
Pulled By: navahgar
fbshipit-source-id: edfc61feaf5efe22d4f367ac718b83b3d0f47cb3
