net/x25: Remove unused x25_terminate_link()

x25_terminate_link() has been unused since the last use was removed
in 2020 by:
commit 7eed751b3b2a ("net/x25: handle additional netdev events")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
Acked-by: Martin Schiller <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/x25.h

···
 int x25_lapb_receive_frame(struct sk_buff *, struct net_device *,
 			   struct packet_type *, struct net_device *);
 void x25_establish_link(struct x25_neigh *);
-void x25_terminate_link(struct x25_neigh *);
 
 /* x25_facilities.c */
 int x25_parse_facilities(struct sk_buff *, struct x25_facilities *,

net/x25/x25_dev.c

···
 	dev_queue_xmit(skb);
 }
 
-void x25_terminate_link(struct x25_neigh *nb)
-{
-	struct sk_buff *skb;
-	unsigned char *ptr;
-
-	if (nb->dev->type != ARPHRD_X25)
-		return;
-
-	skb = alloc_skb(1, GFP_ATOMIC);
-	if (!skb) {
-		pr_err("x25_dev: out of memory\n");
-		return;
-	}
-
-	ptr  = skb_put(skb, 1);
-	*ptr = X25_IFACE_DISCONNECT;
-
-	skb->protocol = htons(ETH_P_X25);
-	skb->dev      = nb->dev;
-	dev_queue_xmit(skb);
-}
-
 void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
 {
 	unsigned char *dptr;