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: G. Liakhovetski <gl@dsa-ac.de>
Signed-off-by: Samuel Ortiz <samuel@sortiz.org>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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);