farsync: fix info leak in ioctl

The fst_get_iface() code fails to initialize the two padding bytes of
struct sync_serial_settings after the ->loopback member. Add an explicit
memset(0) before filling the structure to avoid the info leak.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
fst_open(struct net_device *dev)
{
	int err;
	struct fst_port_info *port;

	port = dev_to_port(dev);
	if (!try_module_get(THIS_MODULE))
          return -EBUSY;

	if (port->mode != FST_RAW) {
		err = hdlc_open(dev);
		if (err) {
			module_put(THIS_MODULE);
			return err;
		}
	}

	fst_openport(port);
	netif_wake_queue(dev);
	return 0;
}

fst_open(struct net_device *dev)
{
	int err;
	struct fst_port_info *port;

	port = dev_to_port(dev);
	if (!try_module_get(THIS_MODULE))
          return -EBUSY;

	if (port->mode != FST_RAW) {
		err = hdlc_open(dev);
		if (err) {
			module_put(THIS_MODULE);
			return err;
		}
	}

	fst_openport(port);
	netif_wake_queue(dev);
	return 0;
}
