rename AudioSystem::newAudioSessionId()

Rename AudioSystem::newAudioSessionId() to
AudioSystem::newAudioUniqueId() as it can be used
also for I/O handles.

Bug: 12378680.
Change-Id: I611ea3b5eb57a4b0774437f477ee87dc4ccc2cc2
diff --git a/services/audiopolicy/AudioPolicyService.h b/services/audiopolicy/AudioPolicyService.h
index 63fc0c3..3769aab 100644
--- a/services/audiopolicy/AudioPolicyService.h
+++ b/services/audiopolicy/AudioPolicyService.h
@@ -437,6 +437,8 @@
         virtual void onAudioPortListUpdate();
         virtual void onAudioPatchListUpdate();
 
+        virtual audio_unique_id_t newAudioUniqueId();
+
      private:
         AudioPolicyService *mAudioPolicyService;
     };