update for new audio.h header location

Change-Id: Ic4c62c4037800802427eb7d3c7f5eb8b25d18876
Signed-off-by: Dima Zavin <dima@android.com>
diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 2673df9..7520ed9 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -39,7 +39,7 @@
 
 #include <cutils/bitops.h>
 
-#include <hardware/audio.h>
+#include <system/audio.h>
 #include <hardware/audio_policy.h>
 
 #define LIKELY( exp )       (__builtin_expect( (exp) != 0, true  ))