arm64: dts: allwinner: a64: add necessary device tree nodes for DE2 CCU

As we have all necessary parts to enable the DE2 CCU on the Allwinner
A64 SoC, add the needed device tree nodes, including the DE2 CCU itself
and the DE2 bus.

The "mixer0-lcd0" simplefb device node is updated to use the DE2 CCU.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>