dt-bindings: display: convert Arm Komeda to DT schema

The Arm Komeda (aka Mali-D71) is a display controller that scans out a
framebuffer and hands a signal to a digital encoder to generate a DVI
or HDMI signal. It supports up to two pipelines, each frame can be
composed of up to four layers.

Convert the existing DT binding to DT schema.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220506140533.3566431-12-andre.przywara@arm.com