watchdog: iTCO_wdt: Fix the parent device

The watchdog's parent is iTCO_wdt (the platform device) not lpc_ich
(the PCI device.) Setting the parent right makes it much easier for
the user to figure out which driver/module is handling the watchdog
device node.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>