arm64: dts: mediatek: mt8390-genio-common: add CPU power supplies

arm64: dts: mediatek: mt8390-genio-common: add CPU power supplies

Mediatek Genio 510-EVK (MT8370) and 700-EVK (MT8390) devicetrees are
missing power supply definitions for all their CPU cores.

On the boards, the big core power is supplied by a MT6319 (sub PMIC),
and little core power by a MT6365 (main PMIC).

MT8370 and MT8390 SoC have the same core type (little cores are ARM
Cortex A55, big ones are A78), the same big core number (2) but MT8390
SoC has more little cores (6) than MT8370 SoC (only 4).

To handle the little core number difference, add in the board common
dtsi the power supply definitions for the common CPU core nodes (0-3,
6 and 7).
The power supplies for the additional MT8390 CPU core nodes (4 and 5)
will be added for the Genio 700 in a separate commit.

Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>