Add #include for use with rbutil

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@12339 a1c6a512-1295-4272-9138-f99709370657
diff --git a/rbutil/ipodpatcher/ipodio.h b/rbutil/ipodpatcher/ipodio.h
index 71cafc5..f2aba26 100644
--- a/rbutil/ipodpatcher/ipodio.h
+++ b/rbutil/ipodpatcher/ipodio.h
@@ -21,6 +21,7 @@
 #define __IPODIO_H
 
 #include <stdint.h>
+#include <unistd.h>
 
 #ifdef __WIN32__
 #include <windows.h>