include missing kernel header

Fixes errors like

| /b/kraj/jlinux-next/poky/build/tmp-eglibc/sysroots/re-64b/usr/include/linux/if_bridge.h:172:20: error: field 'ip6' has incomplete type
| In file included from ../libbridge/libbridge.h:24:0,

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Upstream-Status: Pending

Index: bridge-utils-1.5/libbridge/libbridge.h
===================================================================
--- bridge-utils-1.5.orig/libbridge/libbridge.h	2011-03-28 17:52:54.000000000 -0700
+++ bridge-utils-1.5/libbridge/libbridge.h	2013-03-04 21:16:25.781188309 -0800
@@ -20,6 +20,7 @@
 #define _LIBBRIDGE_H
 
 #include <sys/socket.h>
+#include <linux/in6.h>
 #include <linux/if.h>
 #include <linux/if_bridge.h>