reduce number of binder calls from mediaserver

Reduce the number of audio port, audio patch and
IO config changed binder calls from mediaserver to
client processes:
- Do not call IO config changed callback if selected
device is the same as previously selected one on a given
audio flinger playback or capture thread.
- Do not call the audio port or audo patch list update
callback on a client if this client as no listener registered.

Bug: 22045560.

Change-Id: If780e105404de79b7cb5c80c27b793ceb6b1c423
diff --git a/include/media/IAudioPolicyService.h b/include/media/IAudioPolicyService.h
index ee462a0..6b93f6f 100644
--- a/include/media/IAudioPolicyService.h
+++ b/include/media/IAudioPolicyService.h
@@ -149,6 +149,8 @@
 
     virtual void registerClient(const sp<IAudioPolicyServiceClient>& client) = 0;
 
+    virtual void setAudioPortCallbacksEnabled(bool enabled) = 0;
+
     virtual status_t acquireSoundTriggerSession(audio_session_t *session,
                                            audio_io_handle_t *ioHandle,
                                            audio_devices_t *device) = 0;