dt-bindings: clock: Add RPMHCC bindings for SM6350

Add bindings and update documentation for clock rpmh driver on SM6350.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210820203243.230157-2-konrad.dybcio@somainline.org


Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>