Use symbolic name for return value in legacy audio policy client

Change-Id: Id27628afcbc4eb2c9bf1313c8376802a47a9596c
diff --git a/services/audiopolicy/service/AudioPolicyClientImplLegacy.cpp b/services/audiopolicy/service/AudioPolicyClientImplLegacy.cpp
index a79f8ae..f30a842 100644
--- a/services/audiopolicy/service/AudioPolicyClientImplLegacy.cpp
+++ b/services/audiopolicy/service/AudioPolicyClientImplLegacy.cpp
@@ -56,7 +56,7 @@
     sp<IAudioFlinger> af = AudioSystem::get_audio_flinger();
     if (af == 0) {
         ALOGW("%s: could not get AudioFlinger", __func__);
-        return 0;
+        return AUDIO_MODULE_HANDLE_NONE;
     }
 
     return af->loadHwModule(name);