libuv: Remove kvm dependency for all BSDs except NetBSD

This dependency is not expressed in upstream libuv.  It was added to
CMake by commit 6a497bb0a3 (libuv: Link with kvm on FreeBSD, 2016-09-08,
v3.7.0-rc1~143^2~1).  It is needed only on NetBSD.

Fixes: #26722