dt-bindings: watchdog: qca,ar7130-wdt: convert txt to yaml

Convert txt file to yaml. Add maintainers from git blame.
Drop qca,ar9330-wdt from example of compatible property
and leave only qca,ar7130-wdt, as description of property
mentioned must be qca,ar7130-wdt.

Signed-off-by: Nik Bune <n2h9z4@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Link: https://lore.kernel.org/r/20231102123234.62350-1-n2h9z4@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>