Clean up allocations in FBGEMM linear (#16985)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16985
These statements were causing some redundant allocations + copying, so I cleaned
them up
Reviewed By: zdevito, wanchaol
Differential Revision: D14031067
fbshipit-source-id: f760fb29a2561894d52a2663f557b3e9ab1653de
