watchdog: sp805_wdt: deassert the reset if available

According to the datasheet, the core has an WDOGRESn input signal that
needs to be deasserted before being operational. Implement it in the
driver.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240221-hisi-wdt-v3-1-9642613dc2e6@outlook.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>