soc: mediatek: reduce code duplication of scpsys_probe across all SoCs

Reduce code duplication of scpsys_probe_mtXXXX across all SoCs using
the more generic scpsys_probe all covering all cases to avoid starting
to bloat the driver when more MediaTek SoCs supported are added.

Suggested-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>