net: netrom: Add missing annotation for nr_node_start()

Sparse reports a warning at nr_node_start()
warning: context imbalance in nr_node_start() - wrong count at exit
The root cause is the missing annotation at nr_node_start()
Add the missing __acquires(&nr_node_list_lock) annotation

Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netrom/nr_route.c

@@ -838,6 +838,7 @@ int nr_route_frame(struct sk_buff *skb, ax25_cb *ax25)
 #ifdef CONFIG_PROC_FS
 
 static void *nr_node_start(struct seq_file *seq, loff_t *pos)
+	__acquires(&nr_node_list_lock)
 {
 	spin_lock_bh(&nr_node_list_lock);
 	return seq_hlist_start_head(&nr_node_list, *pos);