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_attach(struct net_device *dev, unsigned short encoding, unsigned short parity)
{
	/*
	 * Setting currently fixed in FarSync card so we check and forget
	 */
	if (encoding != ENCODING_NRZ || parity != PARITY_CRC16_PR1_CCITT)
		return -EINVAL;
	return 0;
}

fst_attach(struct net_device *dev, unsigned short encoding, unsigned short parity)
{
	/*
	 * Setting currently fixed in FarSync card so we check and forget
	 */
	if (encoding != ENCODING_NRZ || parity != PARITY_CRC16_PR1_CCITT)
		return -EINVAL;
	return 0;
}
