hal: Enable proxy feature flag

Enable afe proxy feature flag.

CRs-Fixed: 1081411
Change-Id: I47c6d17ba5d76abd5debb8a299b042716845021c
diff --git a/hal/Makefile.am b/hal/Makefile.am
index e72d350..0c5c65f 100644
--- a/hal/Makefile.am
+++ b/hal/Makefile.am
@@ -152,6 +152,10 @@
 AM_CFLAGS += -DAPTX_DECODER_ENABLED
 endif
 
+if AFE_PROXY
+AM_CFLAGS += -DAFE_PROXY_ENABLED
+endif
+
 h_sources = audio_extn/audio_defs.h \
             audio_extn/audio_extn.h \
             audio_hw.h \