dt-bindings: watchdog: cnxt,cx92755-wdt: convert txt to yaml

Convert txt file to yaml.
Add maintainers list.

Signed-off-by: Nik Bune <n2h9z4@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20231023202622.18558-1-n2h9z4@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>