dts: boards: Add bindings and nodes for the rocktech lcd module

Adds device tree bindings and nodes for the rocktech lcd module used on
imx rt boards. The use of port, endpoint, and remote-endpoint properties
follow what is currently done in linux, but they are not yet used in
zephyr because some additional plumbing is needed in the
extract_dts_includes.py script.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>