match int8 quantization of nnpi (#41094)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41094
mimic nnpi's quantization operations
removed redundant int8 test
Test Plan: ran FC with sizes up to 5, running bigger sizes
Reviewed By: venkatacrc
Differential Revision: D22420537
fbshipit-source-id: 91211c8a6e4d3d3bec2617b758913b44aa44b1b1
