hammerhead: Add offload properties

 * Set fragment size (same as default)
 * Enable gapless playback with offloaded streams
 * Enable offloading for AV (but not streaming AV!)

Change-Id: I1b0f8115bc880bd89f5a0c8ed13e4b54d38e0867
hh: Disable gapless by default

 * Audio driver will enable as necessary. Leaving it on always
   causes issues in some apps like Pandora.

Change-Id: I59a732577c3a4a61c8949498101b4b5bae0998ce