soc: mediatek: SVS: add monitor mode

SVS monitor mode is based on different thermal temperature
to provide suitable SVS bank voltages.
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/20220516004311.18358-5-roger.lu@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>