dt-bindings: rng: Convert iProc RNG200 to YAML

Convert the Broadcom iProc RNG200 HWRNG Device Tree binding to YAML to
help with validation.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20211208003727.3596577-11-f.fainelli@gmail.com


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