enum: Don't directly include enum.h

To allow enum.h to depend on utils.h definitions, avoid its direct inclusion.
Instead include utils.h, which includes enum.h as well.

src/libsimaka/simaka_message.h

@@ -26,7 +26,7 @@
 #ifndef SIMAKA_MESSAGE_H_
 #define SIMAKA_MESSAGE_H_
 
-#include <utils/enum.h>
+#include <utils/utils.h>
 #include <eap/eap.h>
 
 #include "simaka_crypto.h"