hamradio/yam: fix info leak in ioctl

The yam_ioctl() code fails to initialise the cmd field
of the struct yamdrv_ioctl_cfg. Add an explicit memset(0)
before filling the structure to avoid the 4-byte info leak.

Signed-off-by: Salva Peiró <speiro@ai2.upv.es>
Signed-off-by: David S. Miller <davem@davemloft.net>
static inline void yam_rx_byte(struct net_device *dev, struct yam_port *yp, unsigned char rxb)
{
	if (yp->rx_len < YAM_MAX_FRAME) {
		unsigned char c = yp->rx_crcl;
		yp->rx_crcl = (chktabl[c] ^ yp->rx_crch);
		yp->rx_crch = (chktabh[c] ^ rxb);
		yp->rx_buf[yp->rx_len++] = rxb;
	}
}

static inline void yam_rx_byte(struct net_device *dev, struct yam_port *yp, unsigned char rxb)
{
	if (yp->rx_len < YAM_MAX_FRAME) {
		unsigned char c = yp->rx_crcl;
		yp->rx_crcl = (chktabl[c] ^ yp->rx_crch);
		yp->rx_crch = (chktabh[c] ^ rxb);
		yp->rx_buf[yp->rx_len++] = rxb;
	}
}
