watchdog: iTCO_wdt: Simplify module init function

The 'ret' variable in iTCO_wdt_init_module() does not add any value;
drop it.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>