arm64: dts: allwinner: a64: Add display pipeline

Allwinner A64 have a display pipeline with 2 mixers/TCONs, the first
TCON is connected to LCD and the second is to HDMI.

The HDMI controller/PHY pair is similar to the one on H3/H5.

Add all required device tree nodes of the display pipeline, including
the TCON0 LCD one and the TCON1 HDMI one.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
[Icenowy: refactor commit message and add 1st pipeline]
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>