dt-bindings: arm: tegra: nvec: Convert to json-schema

Convert the NVIDIA embedded controller bindings from the free-form text
format to json-schema.

Acked-by: Marc Dietrich <marvin24@gmx.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>