arm64: dts: allwinner: a64: Add MIPI DSI pipeline

Add MIPI DSI pipeline for Allwinner A64.

- dsi node, with A64 compatible since it doesn't support
  DSI_SCLK gating unlike A33
- dphy node, with A64 compatible with A33 fallback since
  DPHY on A64 and A33 is similar
- finally, attach the dsi_in to tcon0 for complete MIPI DSI

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Merlijn Wajer <merlijn@wizzup.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>