This patch documents the device tree bindings of the BA431 hardware
random number generator.

This IP is for instance present in the Viper OEM boards sold by Silex
Insight.
Signed-off-by: Olivier Sobrie <olivier.sobrie@silexinsight.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>