arm64: dts: qcom: sc8280xp: add rng device tree node

Add the necessary device tree node for qcom,prng-ee so we can use the
hardware random number generator. This functionality was tested on a
SA8540p automotive development board using kcapi-rng from libkcapi.

Signed-off-by: Brian Masney <bmasney@redhat.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230103182229.37169-11-bmasney@redhat.com