Fix undefined defines resulting from r3482, which led to libpayload
lacking output functionality.

Signed-off-by: Ulf Jordan <jordan@chalmers.se>

Index: libpayload/include/libpayload.h
===================================================================
--- libpayload/include/libpayload.h	(revision 3493)
+++ libpayload/include/libpayload.h	(arbetskopia)
@@ -30,6 +30,7 @@
 #ifndef _LIBPAYLOAD_H
 #define _LIBPAYLOAD_H
 
+#include <config.h>
 #include <stddef.h>
 #include <arch/types.h>
 #include <arch/io.h>