dt-bindings: crypto: ccree: Convert to json-schema

Convert the Arm TrustZone CryptoCell cryptographic engine Device Tree
binding documentation to json-schema.

Document missing properties.
Update the example to match reality.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/ab361a862755e281f5fef67b3f678d66ae201781.1623413974.git.geert+renesas@glider.be