alsa_sound: Fix audio over Miracast

 * We're not using QC's proprietary WFD solution, so pick the remote
   submix instead of the proxy.

Change-Id: Ie32a4591a27f17e2a1d0b87b5f5a7b8b320ff169
Merge remote-tracking branch 'upstream/cm-10.2' into cm-10.2