dt-bindings: display: amlogic, meson-vpu: convert to yaml

Now that we have the DT validation in place, let's convert the device tree
bindings for the Amlogic Display Controller over to YAML schemas.

The original example has a leftover "dmc" memory cell, that has been
removed in the yaml rewrite.

The port connection table has been dropped in favor of a description
of each port.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808085522.21950-3-narmstrong@baylibre.com