hal: add feature flag to enable instance id support

Add feature flag to enable instance id support for
non-android builds.

Change-Id: I4ab3ab854f557ba63dae60eada8ef951e9d2dced
diff --git a/hal/Makefile.am b/hal/Makefile.am
index 46882f1..995622d 100644
--- a/hal/Makefile.am
+++ b/hal/Makefile.am
@@ -204,6 +204,10 @@
 AM_CFLAGS += -DCUSTOM_STEREO_ENABLED
 endif
 
+if INSTANCE_ID
+AM_CFLAGS += -DINSTANCE_ID_ENABLED
+endif
+
 h_sources = audio_extn/audio_defs.h \
             audio_extn/audio_extn.h \
             audio_hw.h \