hal: update GKI flag

Update GKI flag as AUDIO_GKI_ENABLED.
Add GKI feature flag check for compress passthru module.
Use reserved variable for flags when GKI is enabled in
compress passthru.

Change-Id: Id6dfadb55590fbdbcebed34c2c235ad2da66a08b
diff --git a/hal/audio_extn/Android.mk b/hal/audio_extn/Android.mk
index 3369196..9384136 100644
--- a/hal/audio_extn/Android.mk
+++ b/hal/audio_extn/Android.mk
@@ -622,6 +622,11 @@
   LOCAL_ADDITIONAL_DEPENDENCIES += $(BOARD_VENDOR_KERNEL_MODULES)
 endif
 
+# Kernel specific feature
+ifeq ($(strip $(AUDIO_FEATURE_ENABLED_GKI)), true)
+    LOCAL_CFLAGS += -DAUDIO_GKI_ENABLED
+endif
+
 LOCAL_HEADER_LIBRARIES += libhardware_headers
 LOCAL_HEADER_LIBRARIES += libsystem_headers
 ifneq ($(filter kona lahaina,$(TARGET_BOARD_PLATFORM)),)