add channels last support for thnn_conv2d (non-dilated) (#49582)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/49582
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D26007050
Pulled By: VitalyFedyunin
fbshipit-source-id: 1289e0687c2459dd4eb8e4ba2efc8266397cfe5f
