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/reverb.c b/post_proc/reverb.c
index d104073..4c7fe25 100644
--- a/post_proc/reverb.c
+++ b/post_proc/reverb.c
@@ -23,7 +23,7 @@
 #include <cutils/list.h>
 #include <cutils/log.h>
 #include <tinyalsa/asoundlib.h>
-#include <audio_effects.h>
+#include <sound/audio_effects.h>
 #include <audio_effects/effect_environmentalreverb.h>
 #include <audio_effects/effect_presetreverb.h>