Include what is needed

Remove old includes.
Header files only include other header files that they directly need themselves.

Change-Id: Ic471386808d9f42ea19ccbd59cb50a5f83a89dd0
diff --git a/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index a6dedec..22d6763 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -20,6 +20,7 @@
 #include <utils/Log.h>
 #include <binder/IServiceManager.h>
 #include <media/AudioSystem.h>
+#include <media/IAudioFlinger.h>
 #include <media/IAudioPolicyService.h>
 #include <math.h>