dt-bindings: watchdog: Add compatible for MediaTek MT8186

Add dt-binding documentation of watchdog for MediaTek MT8186 SoC.

Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220301054405.25021-2-rex-bc.chen@mediatek.com


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