watchdog: rtd119x_wdt: Fix remove function

The driver registers the watchdog with devm_watchdog_register_device() but
still calls watchdog_unregister_device() on remove. Since clocks have to
be stopped when removing the driver, after the watchdog device has been
unregistered, we can not drop the call to watchdog_unregister_device().
Use watchdog_register_device() to register the watchdog.

Fixes: 2bdf6acb ("watchdog: Add Realtek RTD1295")
Cc: Andreas Färber <afaerber@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>