dt-bindings: crypto: qcom,prng: document support for SA8255p

Document SA8255p compatible for the True Random Number Generator.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Nikunj Kela <quic_nkela@quicinc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>