dt-bindings: rng: hisi-rng: convert to DT schema

Convert the Devicetree binding documentation for hisilicon,hip04-rng
and hisilicon,hip05-rng from plain text to YAML.

Signed-off-by: Kael D'Alcamo <dev@kael-k.io>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>