[X.25]: Adds /proc/sys/net/x25/x25_forward to control forwarding.

echo "1" > /proc/sys/net/x25/x25_forward 
To turn on x25_forwarding, defaults to off
Requires the previous patch.

Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/x25/sysctl_net_x25.c b/net/x25/sysctl_net_x25.c
index aabda59..2b2e7fd 100644
--- a/net/x25/sysctl_net_x25.c
+++ b/net/x25/sysctl_net_x25.c
@@ -73,6 +73,14 @@
 		.extra1 =	&min_timer,
 		.extra2 =	&max_timer,
 	},
+	{
+		.ctl_name =	NET_X25_FORWARD,
+		.procname =	"x25_forward",
+		.data = 	&sysctl_x25_forward,
+		.maxlen = 	sizeof(int),
+		.mode = 	0644,
+		.proc_handler = &proc_dointvec,
+	},
 	{ 0, },
 };