watchdog: mediatek: mt7988: add wdt support

Add support for watchdog and reset generator unit of the MediaTek
MT7988 SoC.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/c0cf5f701801cce60470853fa15f1d9dced78c4f.1700504385.git.daniel@makrotopia.org


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