hal: add split A2DP sink support

- Add changes to support BT IPC sink library.
- Add mixer control support to send decoder configuration for
  split A2DP sink usecase.
- Add hw loopback support for split A2DP sink usecase.

Change-Id: I3b015385ce1fdd5c0cbf512fe06b73143a32ae2d
diff --git a/hal/Makefile.am b/hal/Makefile.am
index 995622d..fe6feb4 100644
--- a/hal/Makefile.am
+++ b/hal/Makefile.am
@@ -187,6 +187,7 @@
 
 if AUDIO_HW_LOOPBACK
 AM_CFLAGS += -DAUDIO_HW_LOOPBACK_ENABLED
+AM_CFLAGS += -DCOMPRESS_METADATA_NEEDED
 c_sources += audio_extn/hw_loopback.c
 endif