dt-bindings: spi: tegra-slink: Convert to json-schema

Convert the Tegra SLINK bindings from the free-form text format to
json-schema.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230705152603.2514235-1-thierry.reding@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>