watchdog: max63xx_wdt: Add device tree probing

This adds device tree probing to the MAX63xx driver so it can be
instantiated from the device tree. We use the generic fwnode-based
method to get to the match data and clean up by constifying the
functions as the match is indeed a const.

Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210714153314.1004147-2-linus.walleij@linaro.org


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