audio: change TARGET_USES_AOSP to TARGET_USES_AOSP_FOR_AUDIO

- add Audio specific Target_AOSP flag
- this will remove Audio dependency on Global Target AOSP flag

Change-Id: I4df84bbacb34756ad1809a34c95d6492e51e3772
diff --git a/Android.mk b/Android.mk
index 4b40d70..e365177 100644
--- a/Android.mk
+++ b/Android.mk
@@ -18,7 +18,7 @@
 include $(MY_LOCAL_PATH)/qahw_api/Android.mk
 endif
 
-ifneq ($(TARGET_USES_AOSP), true)
+ifneq ($(TARGET_USES_AOSP_FOR_AUDIO), true)
 include $(MY_LOCAL_PATH)/audiod/Android.mk
 endif