cpufreq: Reset cpu-boost to upstream

This reverts 6f42fce2531, make boost thread start/stoppable.
cpufreq: cpu-boost: Use hotplug thread infrastructure

Before this patch, thread migration ran in uninterruptible threads.
Use the relatively new hotplug thread infrastructure with parked
threads to reduce cpu load (x4).
cpufreq: ondemand: Use hotplug thread infrastructure

The dbs_sync threads caused considerable load, even when ondemand
wasn't even active. Use the hotplug thread infrastructure to park
the threads.
msm: mdss: Use interruptible threads

Based on @cyanogens findings, use interruptible threads to reduce
cpu load.