dt-bindings: arm: samsung: Convert Samsung board/soc bindings to json-schema

Convert Samsung S5P and Exynos SoC bindings to DT schema format using
json-schema.  This is purely conversion of already documented bindings
so it does not cover all of DTS in the Linux kernel (few S5P/Exynos and
all S3C are missing).

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