dt-bindings: clock: Refine i.MX8MN clock binding

  '#clock-cells':

    const: 1

    description: |

    description:

      The clock consumer should specify the desired clock by having the clock

      ID in its "clocks" phandle cell. See include/dt-bindings/clock/imx8mn-clock.h

      for the full list of i.MX8M Nano clock IDs.

  - |

    clk: clock-controller@30380000 {

        compatible = "fsl,imx8mn-ccm";

        reg = <0x0 0x30380000 0x0 0x10000>;

        reg = <0x30380000 0x10000>;

        #clock-cells = <1>;

        clocks = <&osc_32k>, <&osc_24m>, <&clk_ext1>,

                 <&clk_ext2>, <&clk_ext3>, <&clk_ext4>;

                      "clk_ext2", "clk_ext3", "clk_ext4";

    };

  # Required external clocks for Clock Control Module node:

  - |

    osc_32k: clock-osc-32k {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency = <32768>;

        clock-output-names = "osc_32k";

    };

    osc_24m: clock-osc-24m {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency = <24000000>;

        clock-output-names = "osc_24m";

    };

    clk_ext1: clock-ext1 {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency = <133000000>;

        clock-output-names = "clk_ext1";

    };

    clk_ext2: clock-ext2 {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency = <133000000>;

        clock-output-names = "clk_ext2";

    };

    clk_ext3: clock-ext3 {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency = <133000000>;

        clock-output-names = "clk_ext3";

    };

    clk_ext4: clock-ext4 {

        compatible = "fixed-clock";

        #clock-cells = <0>;

        clock-frequency= <133000000>;

        clock-output-names = "clk_ext4";

    };

...