Fix build.

Change-Id: I9c76b9cffd53c23b2c3c1bb90cfa3265b711ddb9
diff --git a/audio/audio.h b/audio/audio.h
index 13fc7cc..ebac629 100644
--- a/audio/audio.h
+++ b/audio/audio.h
@@ -26,6 +26,7 @@
 
 #include "config-host.h"
 #include "qemu-queue.h"
+#include "qemu-common.h"  /* For QEMUTimer */
 
 typedef void (*audio_callback_fn) (void *opaque, int avail);