dt-bindings: watchdog: samsung-wdt: Add exynos990-wdt compatible

Add a dt-binding compatible for the Exynos990 Watchdog timer.
This watchdog is compatible with the GS101/Exynos850 design, as
such it requires the cluster-index and syscon-phandle properties
to be present. It also contains a cl2 cluster, as such the
cluster-index property has been expanded.

Signed-off-by: Igor Belwon <igor.belwon@mentallysanemainliners.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20250420-wdt-resends-april-v1-1-f58639673959@mentallysanemainliners.org


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