MediaTek devicetree/bindings warnings sanitization

Merge series from Julien Massot <julien.massot@collabora.com>:

This patch series continues the effort to address Device Tree validation
warnings for MediaTek platforms, with a focus on MT8183. It follows the
initial cleanup series by Angelo
(https://www.spinics.net/lists/kernel/msg5780177.html).

The patches in this set eliminate several of the remaining warnings by
improving or converting DT bindings to DT schema, adding missing properties,
and updating device tree files accordingly.