[IrDA]: irttp_dup spin_lock initialisation

Without this initialization one gets

kernel BUG at kernel/rtmutex_common.h:80!

This patch should also be included in the -stable kernel.
Signed-off-by: NG. Liakhovetski <gl@dsa-ac.de>
Signed-off-by: NSamuel Ortiz <samuel@sortiz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/irda/irttp.c

@@ -1455,6 +1455,7 @@ struct tsap_cb *irttp_dup(struct tsap_cb *orig, void *instance)
 
 	/* Not everything should be copied */
 	new->notify.instance = instance;
+	spin_lock_init(&new->lock);
 	init_timer(&new->todo_timer);
 
 	skb_queue_head_init(&new->rx_queue);