audio policy: add ECHO_REFERENCE to virtual audio sources

When ECHO_REFERENCE audio source was added, it was omitted
from the list of virtual audio sources (sources protected by privileged
permission not accessing the mic). This prevents from capturing echo
reference at the same time as the input from mic.

Bug: 154639757
Test: test app on yukawa
Change-Id: Ib12e8c817dec7c3f4d3f3f7e7403330c88cead52

services/audiopolicy/service/AudioPolicyService.cpp

@@ -676,6 +676,7 @@ bool AudioPolicyService::isVirtualSource(audio_source_t source)
         case AUDIO_SOURCE_VOICE_CALL:
         case AUDIO_SOURCE_REMOTE_SUBMIX:
         case AUDIO_SOURCE_FM_TUNER:
+        case AUDIO_SOURCE_ECHO_REFERENCE:
             return true;
         default:
             break;