arm64: dts: qcom: sm6350: Add RPMHCC node

Add RPMHCC node to allow for referencing RPMH-controlled clocks in other
nodes.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210923162204.21752-4-konrad.dybcio@somainline.org