Remove some unnecessary code in Onnxifi (#39197)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39197
Pull Request resolved: https://github.com/pytorch/glow/pull/4552
Clean up some code to prepare support for quantized output in Onnxifi.
Reviewed By: jfix71
Differential Revision: D21770855
fbshipit-source-id: 8ecfd675846e3a42a80fd133e5eaa8dad0445bd3
