dt-bindings: clock: Document the parent clocks

With clock parent data scheme we must specify the parent clocks for the
rpmhcc nodes. So describe the parent clock for rpmhcc in the bindings.

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lkml.kernel.org/r/20190826173120.2971-2-vkoul@kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/qcom,rpmh-clk.txt

@@ -9,6 +9,9 @@ Required properties :
 - compatible : shall contain "qcom,sdm845-rpmh-clk"
 
 - #clock-cells : must contain 1
+- clocks: a list of phandles and clock-specifier pairs,
+	  one for each entry in clock-names.
+- clock-names: Parent board clock: "xo".
 
 Example :