dt-bindings: interconnect: qcom,rpmh: Add SM8250 QUP virt

Document the QUP virtual bus on SM8250.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230703-topic-8250_qup_icc-v2-1-9ba0a9460be2@linaro.org


Signed-off-by: Georgi Djakov <djakov@kernel.org>