audio: Add pause support for hardware omx component

- ADSP doesn't enter sleep state after wma playback is paused
  and power suspended.
- No support for NT session pause in case of hardware component.
  NT session need to be paused to put ADSP into power collapse.
- Add support of pause in stagefright to ensure device enters
  suspend mode. Also add intermediate states to avoid concurrency
  issues between read and pause.

Change-Id: I41b946b8c8805e6ee303646b63513b5b16514ef6