devicetree: bindings: Deprecate property, update example

    in clock-names.

  - clock-names: must contain "fck" for the functional clock.

  - renesas,channels-mask: bitmask of the available channels.

  - renesas,channels-mask: <deprecated>, information kept in device driver.

Example: R8A7790 (R-Car H2) CMT0 node

	CMT0 on R8A7790 implements hardware channels 5 and 6 only and names

	them channels 0 and 1 in the documentation.

Example: R8A7790 (R-Car H2) CMT0 and CMT1 nodes

	cmt0: timer@ffca0000 {

		compatible = "renesas,cmt-48-r8a7790", "renesas,cmt-48-gen2";

		compatible = "renesas,cmt0-r8a7790", "renesas,rcar-gen2-cmt0";

		reg = <0 0xffca0000 0 0x1004>;

		interrupts = <0 142 IRQ_TYPE_LEVEL_HIGH>,

			     <0 142 IRQ_TYPE_LEVEL_HIGH>;

		clocks = <&mstp1_clks R8A7790_CLK_CMT0>;

		clock-names = "fck";

	};

		renesas,channels-mask = <0x60>;

	cmt1: timer@e6130000 {

		compatible = "renesas,cmt1-r8a7790", "renesas,rcar-gen2-cmt1";

		reg = <0 0xe6130000 0 0x1004>;

		interrupts = <0 120 IRQ_TYPE_LEVEL_HIGH>,

			     <0 121 IRQ_TYPE_LEVEL_HIGH>,

			     <0 122 IRQ_TYPE_LEVEL_HIGH>,

			     <0 123 IRQ_TYPE_LEVEL_HIGH>,

			     <0 124 IRQ_TYPE_LEVEL_HIGH>,

			     <0 125 IRQ_TYPE_LEVEL_HIGH>,

			     <0 126 IRQ_TYPE_LEVEL_HIGH>,

			     <0 127 IRQ_TYPE_LEVEL_HIGH>;

		clocks = <&mstp3_clks R8A7790_CLK_CMT1>;

		clock-names = "fck";

	};