hammerhead: Optimize I/O scheduling

Inspired by bacon. We aren't suffering from slowdowns
during bootanim, anyway this is the right way to do it.

Change-Id: Icf3d9d6e52926012a4b7fdfdc1456a37ad782e71
hammerhead: Make audio not suck anymore.

 * Add support for additional low-power offload modes
 * Enable gapless playback support
 * Enable 24-bit playback
 * Enable the compander for increased dynamic range on headphones
   and speaker output

Change-Id: If8cae7e940ba753d8b155017b15239bb49616b72