audio: fix switch to break or use FALLTHROUGH_INTENDED

Test: compile, sanity
Bug: 117509050
Change-Id: I9439f201b3d1f4485ab698d7bed063a02f17f8f0
diff --git a/services/audiopolicy/enginedefault/src/Engine.cpp b/services/audiopolicy/enginedefault/src/Engine.cpp
index c76326a..69395f3 100644
--- a/services/audiopolicy/enginedefault/src/Engine.cpp
+++ b/services/audiopolicy/enginedefault/src/Engine.cpp
@@ -186,6 +186,7 @@
         return STRATEGY_DTMF;
     default:
         ALOGE("unknown stream type %d", stream);
+        FALLTHROUGH_INTENDED;
     case AUDIO_STREAM_SYSTEM:
         // NOTE: SYSTEM stream uses MEDIA strategy because muting music and switching outputs
         // while key clicks are played produces a poor result