ACodec: Support for dynamic port reconfig

- On port settings changed first flush output port
- Move ACodec to new state called FlushingOutputState
- Flush all output buffers, wait till all decoded buffers
  are rendered
- Then disable output port, and allocate output buffers
  with new resolution, and reset native window

Change-Id: Iafa266371ed2a87b909fbcb4eeae6b64208df617