arm64: dts: qcom: Add pmu node to sdm845

Add the CPU PMU on sdm845 to get perf support for hardware events.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>