dt-bindings: watchdog: arm,sp805: document the reset signal

The reset signal needs to be deasserted before operation of sp805
module. Document in the binding.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240221-hisi-wdt-v3-2-9642613dc2e6@outlook.com


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