hal: compilation fix for extended feature flags

- Fix compilation error for offload, Dolby,
  HDMI pass through, FLAC decoder, and hardware
  accelerated effects when extended feature
  flags are disabled.

Change-Id: If64d5fa5d124b42d40d7e123b887db8e0a5d7426
diff --git a/post_proc/effect_api.c b/post_proc/effect_api.c
index 2fb79ed..7aef997 100644
--- a/post_proc/effect_api.c
+++ b/post_proc/effect_api.c
@@ -60,7 +60,7 @@
 #include <sound/audio_effects.h>
 #include <sound/devdep_params.h>
 #include <linux/msm_audio.h>
-
+#include <errno.h>
 #include "effect_api.h"
 
 #ifdef DTS_EAGLE