hh: Better scaling values

 * Default slack is too long and boost is too high, these values
   collide. Fix them.
 * Set a better timer_rate to reduce jitter

Change-Id: Id99c1642ca38d184e75d09bd3afc71951a8801c0
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
hammerhead: Disable forced use of triple framebuffers

 * This can cause additional input latency and isn't really
   needed on this hardware.

Change-Id: I662915c08f9e8b9eef609319806feda880acc7a5
hammerhead: Enable use of FFMPEG codecs for extended formats

Change-Id: I1dc66749b6b5548c3617cbbfff389abc3d319562