soc: mediatek: SVS: add mt8192 SVS GPU driver

mt8192 SVS GPU uses 2-line (high/low bank) HW architecture to provide
bank voltages. High bank helps update higher frequency's voltage
and low bank helps update lower frequency's 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/20220516004311.18358-8-roger.lu@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>