dt-bindings: watchdog: xlnx,versal-wwdt: Add versal watchdog

dt-bindings: watchdog: xlnx,versal-wwdt: Add versal watchdog

Versal watchdog IP uses window watchdog mode. Window watchdog
timer(WWDT) contains closed(first) and open(second) window with
32 bit width. Write to the watchdog timer within predefined window
periods of time. This means a period that is not too soon and
a period that is not too late.

Add devicetree bindings for versal window watchdog device.

Signed-off-by: Srinivas Neeli <srinivas.neeli@amd.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lkml.kernel.org/r/20230420104231.2243079-3-srinivas.neeli@amd.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>