locate: change from BSD-4-clause to BSD-3-clause

We have the authorization from the University of California to remove
the advertising clause for a while, wosch@ who also hold a copyright
on this code also approved the relicensing

Approved by: wosch@
MFC after: 3 days

(cherry picked from commit 389844c058ec1ab69bb506601ed673fdd4e4d12b)