spdx: Simplify BSD-2-Clause AND BSD-2-Clause
After removing the -FreeBSD and -NetBSD, we're left with a nuber of
BSD-2-Clause AND BSD-2-Clause, so tidy that up.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix
(cherry picked from commit eebd9d53665e1b691ffada910b940b37b6f62cc4)