hal: add support for compress passthrough

- Add support for compress passthrough.

Change-Id: I4934470ac8b23cb8de9b2d7d1b0014afe74b5a27
diff --git a/hal/Android.mk b/hal/Android.mk
index c1e122d..9888396 100644
--- a/hal/Android.mk
+++ b/hal/Android.mk
@@ -227,6 +227,12 @@
 
 ifeq ($(strip $(AUDIO_FEATURE_ENABLED_HDMI_PASSTHROUGH)),true)
     LOCAL_CFLAGS += -DHDMI_PASSTHROUGH_ENABLED
+    LOCAL_SRC_FILES += audio_extn/passthru.c
+endif
+
+ifeq ($(strip $(AUDIO_FEATURE_ENABLED_KEEP_ALIVE)),true)
+    LOCAL_CFLAGS += -DKEEP_ALIVE_ENABLED
+    LOCAL_SRC_FILES += audio_extn/keep_alive.c
 endif
 
 ifeq ($(strip $(AUDIO_FEATURE_ENABLED_SOURCE_TRACKING)),true)