arm64: dts: renesas: r8a774c0: Add display output support

The RZ/G2E (a.k.a. R8A774C0) has one RGB output and two LVDS
outputs connected to DU.
This patch add support for DU, LVDS encoders, VSP and FCP.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>