MFC r327056: Use resume_cpus() instead of restart_cpus() to resume from ACPI suspension.

The merge needed fixing because common x86 code changed by the original
commit is still split between i386 and amd64 in this branch.

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.

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.