wanxl: fix info leak in ioctl

The wanxl_ioctl() 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: Salva Peiró <speiro@ai2.upv.es>
Signed-off-by: David S. Miller <davem@davemloft.net>
static inline dma_addr_t pci_map_single_debug(struct pci_dev *pdev, void *ptr,
					      size_t size, int direction)
{
	dma_addr_t addr = pci_map_single(pdev, ptr, size, direction);
	if (addr + size > 0x100000000LL)
		pr_crit("%s: pci_map_single() returned memory at 0x%llx!\n",
			pci_name(pdev), (unsigned long long)addr);
	return addr;
}

static inline dma_addr_t pci_map_single_debug(struct pci_dev *pdev, void *ptr,
					      size_t size, int direction)
{
	dma_addr_t addr = pci_map_single(pdev, ptr, size, direction);
	if (addr + size > 0x100000000LL)
		pr_crit("%s: pci_map_single() returned memory at 0x%llx!\n",
			pci_name(pdev), (unsigned long long)addr);
	return addr;
}
