dt-bindings: crypto: qcom-qce: document the SC7280 crypto engine

Document the crypto engine on the SM7280 Platform.

Signed-off-by: Om Prakash Singh <quic_omprsing@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>