Gnu tools need to include what they use.

The if_bridge.h uses in6, but didn't include the header for the struct
which causes bridge-utils to fail to compile.

Change-Id: I4af45499b48f0f4f15bd08bca76e284a98ed0dc7
diff --git a/arm-linux-gnueabihf/sys-root/usr/include/linux/if_bridge.h b/arm-linux-gnueabihf/sys-root/usr/include/linux/if_bridge.h
index aac8b8c..c68b115 100644
--- a/arm-linux-gnueabihf/sys-root/usr/include/linux/if_bridge.h
+++ b/arm-linux-gnueabihf/sys-root/usr/include/linux/if_bridge.h
@@ -14,6 +14,7 @@
 #define _LINUX_IF_BRIDGE_H
 
 #include <linux/types.h>
+#include <linux/in6.h>
 
 #define SYSFS_BRIDGE_ATTR	"bridge"
 #define SYSFS_BRIDGE_FDB	"brforward"