Merge r264984

Merge r264984

Retire smp_active.  It was racey and caused demonstrated problems with
the cpufreq code.  Replace its use with smp_started.  There's at least
one userland tool that still looks at the kern.smp.active sysctl, so
preserve it but point it to smp_started as well.

Obtained from:	Netflix, Inc.

git-svn-id: svn://svn.freebsd.org/base/stable/10@265606 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f