post_proc: include audio_effects.h from kernel exported headers

Currently, audio_effects.h header file is included with reference
to the absolute path. Instead, reference it from the kernel
exported headers.

Change-Id: I83880e0947e8b6a334b11c952fe8182b49ef5090
diff --git a/post_proc/effect_api.c b/post_proc/effect_api.c
index a2e4f45..0b77969 100644
--- a/post_proc/effect_api.c
+++ b/post_proc/effect_api.c
@@ -33,7 +33,7 @@
 #include <stdbool.h>
 #include <cutils/log.h>
 #include <tinyalsa/asoundlib.h>
-#include <audio_effects.h>
+#include <sound/audio_effects.h>
 
 #include "effect_api.h"