Revert D30526034: [pytorch][PR] compute reduction intermediate buffer size in elements
Test Plan: revert-hammer
Differential Revision:
D30526034 (https://github.com/pytorch/pytorch/commit/e69a1398cbe534874060460faf36af21d24ce6e7)
Original commit changeset: 0aca7f887974
fbshipit-source-id: a22472723818d6fe0c11a6e134080df1ac408038
