audio: improve logging.

- log msgs showing device switches
- log msgs shoing open/close of input/output streams

Change-Id: Ic6fbedc4b48db72bf2cf8af38ade0e3e80243640
audio: Increased mute wait for USB Playback

- Sometimes, when touch tones are played over USB Headset
  glitch is heard. This issue is seen when startOuput
  is called for touch tone after the device goes into
  standby

- Fix is to increase the mute wait during starting of the
  output to give additional time for the proxy device to
  come up

CRs-Fixed: 615405

Change-Id: I37b772582058ec6939ca13067a31360a4de9784b
Audio: Add new format and property for PCM offload

- Add string to enum method for PCM offload 16/24 bit
  formats

Change-Id: I8dcc2e35e1c8635a5b8f6f8de15167a40b842767