Fix bazel-test linking issue (#36157)
Summary:
Move `src/GenerateI8Depthwise.cc` from `fbgemm_baze` to `fbgemm_avx2`, because bazel hides unsued functions across the libraries
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36157
Differential Revision: D20900955
Pulled By: malfet
fbshipit-source-id: a180c8b54ca39bc076f42f2a740fd3b7f20750dc
