Add missing include for IFF_BROADCAST to fix build

(cherry picked from commit cfbb4ac47fb065c888b63b03a5697d24c9c5952e)

Change-Id: I03411d12ef4f45fe0c0c14dd6f546108e272da93
diff --git a/config.h b/config.h
index b6d9ae1..e31a81d 100644
--- a/config.h
+++ b/config.h
@@ -19,6 +19,7 @@
 #define __CONFIG_H__
 
 #include <netinet/in.h>
+#include <linux/if.h>
 
 #define DEFAULT_IPV4_LOCAL_SUBNET "192.0.0.4"
 #define DEFAULT_IPV4_LOCAL_PREFIXLEN "29"