Make vec512 bfloat16 map function clang-Wall clean (#69707)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69707
`const` modifier for `__m512` return value doesn't make much sense
Test Plan: Imported from OSS
Reviewed By: r-barnes
Differential Revision: D32997008
Pulled By: malfet
fbshipit-source-id: fb98659713fe2a23cc702252c0655106687f0dbf
