watchdog: w83697hf_wdt: return ENODEV if no device was found

Most WDT driver modules return ENODEV during modprobe if
no valid device was found, but w83697hf_wdt returns EIO.

Let w83697hf_wdt return ENODEV.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>