dt-bindings: watchdog: convert meson-wdt.txt to dt-schema

Convert the Amlogic Meson6 SoCs Watchdog timer bindings to dt-schema.

Take in account the used interrupts property.

The "amlogic,meson8-wdt" representation has been simplified
since there's no users of this compatible used along the
"amlogic,meson6-wdt".

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20221117-b4-amlogic-bindings-convert-v3-3-e28dd31e3bed@linaro.org


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