dt-bindings: watchdog: alphascale-asm9260: convert to DT schema

Makes alphascale-asm9260 dt bindings adhere to the dt json-schema
by replacing txt file with yaml file.

Signed-off-by: Om Parikh <hack3r-0m@proton.me>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230418051446.24288-1-hack3r-0m@proton.me


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