[AX25] ax25_ds_timer: use mod_timer instead of add_timer

This patch changes current use of: init_timer(), add_timer()
and del_timer() to setup_timer() with mod_timer(), which
should be safer anyway.

Reported-by: Jann Traschewski <jann@gmx.de>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ax25/ax25_ds_timer.c b/net/ax25/ax25_ds_timer.c
index c4e3b02..2ce79df 100644
--- a/net/ax25/ax25_ds_timer.c
+++ b/net/ax25/ax25_ds_timer.c
@@ -40,13 +40,10 @@
  *	1/10th of a second.
  */
 
-static void ax25_ds_add_timer(ax25_dev *ax25_dev)
+void ax25_ds_setup_timer(ax25_dev *ax25_dev)
 {
-	struct timer_list *t = &ax25_dev->dama.slave_timer;
-	t->data		= (unsigned long) ax25_dev;
-	t->function	= &ax25_ds_timeout;
-	t->expires	= jiffies + HZ;
-	add_timer(t);
+	setup_timer(&ax25_dev->dama.slave_timer, ax25_ds_timeout,
+		    (unsigned long)ax25_dev);
 }
 
 void ax25_ds_del_timer(ax25_dev *ax25_dev)
@@ -60,10 +57,9 @@
 	if (ax25_dev == NULL)		/* paranoia */
 		return;
 
-	del_timer(&ax25_dev->dama.slave_timer);
 	ax25_dev->dama.slave_timeout =
 		msecs_to_jiffies(ax25_dev->values[AX25_VALUES_DS_TIMEOUT]) / 10;
-	ax25_ds_add_timer(ax25_dev);
+	mod_timer(&ax25_dev->dama.slave_timer, jiffies + HZ);
 }
 
 /*