audio policy: binder calls for dynamic audio policy mixes

Add binder calls to register and unregister dynamic mixes
to AudioPolicyManager.

Bug: 16009464.

Change-Id: I4ef38166d0cfc88c984970969380d0cd6eb083ac
diff --git a/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 96f1ade..9cae21c 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -958,6 +958,12 @@
     return aps->getPhoneState();
 }
 
+status_t AudioSystem::registerPolicyMixes(Vector<AudioMix> mixes, bool registration)
+{
+    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();
+    if (aps == 0) return PERMISSION_DENIED;
+    return aps->registerPolicyMixes(mixes, registration);
+}
 
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