watchdog: gpio_wdt: Make use of device properties

Convert the module to be property provider agnostic and allow
it to be used on non-OF platforms.

Include mod_devicetable.h explicitly to replace the dropped of.h
which included mod_devicetable.h indirectly.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230925123543.2945710-1-andriy.shevchenko@linux.intel.com


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