hal: Add speaker backend case handling

* Some devices route their speakers through a different backend. Allow
  speaker use cases to be routed separately in this case.

Change-Id: I6bcaa4a0b72d2fc60ae02d4f49cfca0fdb55405f
hal: Correct PCM offload fragment size

- Correct the fragment size to use bytes instead of bits
  per sample
- Use 80ms as pcm offload buffer duration for video streaming
  usecases and 1 sec for video + audio usecases

Change-Id: Iec8e24c2b158368742a55710a46da94ce5d3c170

Conflicts:
	hal/msm8974/platform.c

Change-Id: Iec8e24c2b158368742a55710a46da94ce5d3c170