ARM: dts: qcom: msm8974: add rpm-stats device node

Add device node for the rpm-stats pseudo device.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220726205355.598874-2-dmitry.baryshkov@linaro.org