Make blend operations clang-Wall clean (#69705)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/69705
Test Plan: Imported from OSS
Reviewed By: r-barnes
Differential Revision: D32997007
Pulled By: malfet
fbshipit-source-id: cbadc44e1e7373800e94b7b2fd2711530854978c
