AwesomePlayer: Separate cache buffer watermarks for offload audio

- Using normal playback cache watermarks for offload playback leads to
cache underruns & buffering pauses resulting in choppy audio.
- Add new properties to define cache hi/low watermarks for offload audio.
- Calculate cache buffer levels only based on size for offload audio.

Change-Id: Idb8c1be351678d57490939187079f452a65aebc3
Signed-off-by: Sridhar Vashist <svashist@motorola.com>