watchdog: iTCO_wdt: Add PMC specific noreboot update api

In some SoCs, setting noreboot bit needs modification to
PMC GC registers. But not all PMC drivers allow other drivers
to memory map their GC region. This could create mem request
conflict in watchdog driver. So this patch adds facility to allow
PMC drivers to pass noreboot update function to watchdog
drivers via platform data.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>