dt-bindings: clock: cdce925: Add regulator documentation

The cdce925 has two separate supply pins. Document the bindings
for them.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Link: https://lkml.kernel.org/r/1561691950-42154-2-git-send-email-preid@electromag.com.au

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

Documentation/devicetree/bindings/clock/ti,cdce925.txt

@@ -24,6 +24,8 @@ Required properties:
 Optional properties:
  - xtal-load-pf: Crystal load-capacitor value to fine-tune performance on a
                  board, or to compensate for external influences.
+- vdd-supply: A regulator node for Vdd
+- vddout-supply: A regulator node for Vddout
 
 For all PLL1, PLL2, ... an optional child node can be used to specify spread
 spectrum clocking parameters for a board.
@@ -41,6 +43,8 @@ Example:
 		clocks = <&xtal_27Mhz>;
 		#clock-cells = <1>;
 		xtal-load-pf = <5>;
+		vdd-supply = <&1v8-reg>;
+		vddout-supply = <&3v3-reg>;
 		/* PLL options to get SSC 1% centered */
 		PLL2 {
 			spread-spectrum = <4>;