dt-bindings: arm: Convert ARM CCI-400 binding to a schema

The ARM CCI-400 Interconnect is supported by Linux thanks to its device
tree binding.

Now that we have the DT validation in place, let's convert the device
tree bindings for that driver over to a YAML schema.

Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210901091852.479202-7-maxime@cerno.tech
Signed-off-by: Rob Herring <robh@kernel.org>