Suppress some unused variable warnings in Sorting.cu and TensorTopK.cu (#70999)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/70999
Test Plan: Sandcastle
Reviewed By: malfet
Differential Revision: D33470240
fbshipit-source-id: 906932cb5f497c77465b70ec9bc6fcb0705719de
