dt-bindings: clock: Update i.MX23 example

Update the i.MX23 clock example to align with MXS AUART binding doc to
avoid below build error:

Documentation/devicetree/bindings/clock/imx23-clock.example.dt.yaml:
   serial@8006c000: clocks: [[4294967295, 32]] is too short
Documentation/devicetree/bindings/clock/imx23-clock.example.dt.yaml:
   serial@8006c000: 'dmas' is a required property
Documentation/devicetree/bindings/clock/imx23-clock.example.dt.yaml:
    serial@8006c000: 'dma-names' is a required property
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1597721685-9280-2-git-send-email-Anson.Huang@nxp.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/clock/imx23-clock.yaml

@@ -87,6 +87,8 @@ examples:
     serial@8006c000 {
         compatible = "fsl,imx23-auart";
         reg = <0x8006c000 0x2000>;
-        interrupts = <24 25 23>;
+        interrupts = <24>;
         clocks = <&clks 32>;
+        dmas = <&dma_apbx 6>, <&dma_apbx 7>;
+        dma-names = "rx", "tx";
     };