dt-bindings: watchdog: Add Maxim MAX63xx bindings

This adds devicetree bindings for the Maxim MAX63xx watchdog
timers.

Cc: devicetree@vger.kernel.org
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210714153314.1004147-1-linus.walleij@linaro.org


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