arm64: dts: mediatek: mt8390-genio-700-evk: Add Display on DSI0

Configure the DSI0 display pipeline and add regulator, pinctrl
and display node to enable the Startek KD070FHFID078 panel found
on the MediaTek Genio 700 EVK.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>