dt-bindings: rng: convert Samsung Exynos TRNG to dtschema

Convert Samsung Exynos SoC True Random Number Generator bindings to DT
schema format using json-schema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210811084306.28740-2-krzysztof.kozlowski@canonical.com


Signed-off-by: Rob Herring <robh@kernel.org>