dt-bindings: clk: meson: add main controller clock input

Add the clock input of the main clock controller
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

Documentation/devicetree/bindings/clock/amlogic,gxbb-clkc.txt

@@ -9,6 +9,9 @@ Required Properties:
 		"amlogic,gxbb-clkc" for GXBB SoC,
 		"amlogic,gxl-clkc" for GXL and GXM SoC,
 		"amlogic,axg-clkc" for AXG SoC.
+- clocks : list of clock phandle, one for each entry clock-names.
+- clock-names : should contain the following:
+  * "xtal": the platform xtal
 
 - #clock-cells: should be 1.
 
@@ -31,6 +34,8 @@ sysctrl: system-controller@0 {
 	clkc: clock-controller {
 		#clock-cells = <1>;
 		compatible = "amlogic,gxbb-clkc";
+		clocks = <&xtal>;
+		clock-names = "xtal";
 	};
 };