soc: mediatek: Add MT2701 scpsys driver

Add scpsys driver for MT2701.

mtk-scpsys now supports MT8173 (arm64) and MT2701 (arm). So it should
be enabled on both arm64 and arm platforms.

Signed-off-by: Shunli Wang <shunli.wang@mediatek.com>
Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>