netrom: Add missing annotation for nr_info_stop()

Sparse reports a warning at nr_info_stop()
warning: context imbalance in nr_info_stop() - unexpected unlock
The root cause is the missing annotation at nr_info_stop()
Add the missing __releases(&nr_list_lock)

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

net/netrom/af_netrom.c

@@ -1242,6 +1242,7 @@ static void *nr_info_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void nr_info_stop(struct seq_file *seq, void *v)
+	__releases(&nr_list_lock)
 {
 	spin_unlock_bh(&nr_list_lock);
 }