soc: mediatek: add scpsys support active_wakeup

Register gpd_dev_ops.active_wakeup function to support keep power
during suspend state. And add flag to each power domain to
decide whether keep power during suspend or not.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Eddie Huang <eddie.huang@mediatek.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>