Add missing AudioPolicy.cpp to Android.mk

Change-Id: Iddafc39affe1082dc437f863b35d82790eca550d
diff --git a/media/libmedia/Android.mk b/media/libmedia/Android.mk
index b91b7d1..6c585fb 100644
--- a/media/libmedia/Android.mk
+++ b/media/libmedia/Android.mk
@@ -58,7 +58,8 @@
     AudioEffect.cpp \
     Visualizer.cpp \
     MemoryLeakTrackUtil.cpp \
-    StringArray.cpp
+    StringArray.cpp \
+    AudioPolicy.cpp
 
 LOCAL_SRC_FILES += ../libnbaio/roundup.c