[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_dev.c b/net/ax25/ax25_dev.c
index 528c874..a7a0e0c 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -82,7 +82,7 @@
 	ax25_dev->values[AX25_VALUES_DS_TIMEOUT]= AX25_DEF_DS_TIMEOUT;
 
 #if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER)
-	init_timer(&ax25_dev->dama.slave_timer);
+	ax25_ds_setup_timer(ax25_dev);
 #endif
 
 	spin_lock_bh(&ax25_dev_lock);