s390: use free_netdev(netdev) instead of kfree()

Freeing netdev without free_netdev() leads to net, tx leaks.
I might lead to dereferencing freed pointer.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

@@
struct net_device* dev;
@@

-kfree(dev)
+free_netdev(dev)
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/ctcm_main.c

@@ -1154,7 +1154,7 @@ static struct net_device *ctcm_init_netdevice(struct ctcm_priv *priv)
 				dev_fsm, dev_fsm_len, GFP_KERNEL);
 	if (priv->fsm == NULL) {
 		CTCMY_DBF_DEV(SETUP, dev, "init_fsm error");
-		kfree(dev);
+		free_netdev(dev);
 		return NULL;
 	}
 	fsm_newstate(priv->fsm, DEV_STATE_STOPPED);
@@ -1165,7 +1165,7 @@ static struct net_device *ctcm_init_netdevice(struct ctcm_priv *priv)
 		grp = ctcmpc_init_mpc_group(priv);
 		if (grp == NULL) {
 			MPC_DBF_DEV(SETUP, dev, "init_mpc_group error");
-			kfree(dev);
+			free_netdev(dev);
 			return NULL;
 		}
 		tasklet_init(&grp->mpc_tasklet2,