hal: make file change to export audio_defs.h

- copy audio_defs.h to out target so that it
  can be included in AOSP code.

Change-Id: I84996dd8821a48a9ec71a1164764bf28b91cd390
diff --git a/hal/Android.mk b/hal/Android.mk
index 73ae361..2556aa0 100644
--- a/hal/Android.mk
+++ b/hal/Android.mk
@@ -171,6 +171,9 @@
     LOCAL_CFLAGS += -DAUXPCM_BT_ENABLED
 endif
 
+LOCAL_COPY_HEADERS_TO   := mm-audio
+LOCAL_COPY_HEADERS      := audio_extn/audio_defs.h
+
 LOCAL_MODULE := audio.primary.$(TARGET_BOARD_PLATFORM)
 
 LOCAL_MODULE_RELATIVE_PATH := hw