dt-bindings: soc: imx8mp-hsio-blk-ctrl: add clock cells

The HSIO blk-ctrl has a internal PLL, which can be used as a reference
clock for the PCIe PHY. Add clock-cells to the binding to allow the
driver to expose this PLL.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-hsio-blk-ctrl.yaml

@@ -39,6 +39,9 @@ properties:
       - const: pcie
       - const: pcie-phy
 
+  '#clock-cells':
+    const: 0
+
   clocks:
     minItems: 2
     maxItems: 2
@@ -85,4 +88,5 @@ examples:
         power-domain-names = "bus", "usb", "usb-phy1",
                              "usb-phy2", "pcie", "pcie-phy";
         #power-domain-cells = <1>;
+        #clock-cells = <0>;
     };