Use devm_add_action_or_reset() to disable the watchdog when the driver
is removed to simplify the code. With this in place, we can use
devm_watchdog_register_device() to register the watchdog, and the removal
function is no longer necessary.

Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230304165653.2179835-2-linux@roeck-us.netSigned-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>