watchdog: Convert iTCO_wdt driver to mfd model

This patch converts the iTCO_wdt driver to use the multi-function device
driver model. It uses resources discovered by the lpc_ich driver, so that
it no longer does its own PCI scanning.

Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>