hammerhead: Configure sync_freq feature

Use the (optimized) sync_freq feature to stop frequency
jumping around, causing jitter. We may now even revert
timer_rate and timer_slack to the previous conservative
values.

Change-Id: Ie479a97d00d02b7f2b9867549848f1c251fcb642
Merge remote-tracking branch 'aokp/kitkat' into sm-4.4