soc: mediatek: SVS: introduce MTK SVS engine

soc: mediatek: SVS: introduce MTK SVS engine

The Smart Voltage Scaling(SVS) engine is a piece of hardware
which calculates suitable SVS bank voltages to OPP voltage table.
Then, DVFS driver could apply those SVS bank voltages to PMIC/Buck
when receiving OPP_EVENT_ADJUST_VOLTAGE.

Signed-off-by: Roger Lu <roger.lu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20220516004311.18358-4-roger.lu@mediatek.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>