bitstream_debug: build related cleanup

Move experimental config from debug_util.c/h to aom_util.mk to avoid
empty object.

Change-Id: Id7978ed6a342262bddaa4df8b53115e750fa1c2c
diff --git a/aom_util/debug_util.h b/aom_util/debug_util.h
index 5cad87c..7c2299a 100644
--- a/aom_util/debug_util.h
+++ b/aom_util/debug_util.h
@@ -17,7 +17,6 @@
 extern "C" {
 #endif
 
-#if CONFIG_BITSTREAM_DEBUG
 /* This is a debug tool used to detect bitstream error. On encoder side, it
  * pushes each bit and probability into a queue before the bit is written into
  * the Arithmetic coder. On decoder side, whenever a bit is read out from the
@@ -35,10 +34,9 @@
 void bitstream_queue_set_skip_write(int skip);
 void bitstream_queue_set_skip_read(int skip);
 void bitstream_queue_set_frame_write(int frame_idx);
-int bitstream_queue_get_frame_write();
+int bitstream_queue_get_frame_write(void);
 void bitstream_queue_set_frame_read(int frame_idx);
-int bitstream_queue_get_frame_read();
-#endif  // CONFIG_BITSTREAM_DEBUG
+int bitstream_queue_get_frame_read(void);
 
 #ifdef __cplusplus
 }  // extern "C"