add AUDIO_EXT_ROUTING_HINT

- audio routing for external source will be passed
  through this property before audio focus is requested.
- Actual routing change should happen only when audio
  focus is changed.
- Supported ext routings are passed through config_string.
  This allows supporting custom routing for specific H/W.

bug: 29601910
Change-Id: If43e2413f9645631477bc4480f45e1d2e5ba5e8c
(cherry picked from commit c5b9436c17362da6be035b73c56c41b897b4261e)
1 file changed