Fix clang warnings in AudioFlinger

Change-Id: I0fa61025c979709ad7d655bc717df5f194b6089e
diff --git a/include/media/AudioEffect.h b/include/media/AudioEffect.h
index 05d834d..f3024b7 100644
--- a/include/media/AudioEffect.h
+++ b/include/media/AudioEffect.h
@@ -36,7 +36,7 @@
 
 // ----------------------------------------------------------------------------
 
-class effect_param_cblk_t;
+struct effect_param_cblk_t;
 
 // ----------------------------------------------------------------------------
 
diff --git a/include/media/AudioRecord.h b/include/media/AudioRecord.h
index 33fa121..7054fd4 100644
--- a/include/media/AudioRecord.h
+++ b/include/media/AudioRecord.h
@@ -26,7 +26,7 @@
 
 // ----------------------------------------------------------------------------
 
-class audio_track_cblk_t;
+struct audio_track_cblk_t;
 class AudioRecordClientProxy;
 
 // ----------------------------------------------------------------------------
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index 3a60217..5a50280 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -27,7 +27,7 @@
 
 // ----------------------------------------------------------------------------
 
-class audio_track_cblk_t;
+struct audio_track_cblk_t;
 class AudioTrackClientProxy;
 class StaticAudioTrackClientProxy;