Revert D25399470: add channels last for MaxPool2d
Test Plan: revert-hammer
Differential Revision:
D25399470 (https://github.com/pytorch/pytorch/commit/f43eb59a68246f914970d2cfa94c7ff41d48ad38)
Original commit changeset: b49b9581f132
fbshipit-source-id: ab8c053964aeecf196f6d932c63ada51a3b7ced8
