Device Tree Clock bindings for arch-rockchip

This binding uses the common clock binding[1].

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt

== Gate clocks ==

The gate registers form a continuos block which makes the dt node
structure a matter of taste, as either all gates can be put into
one gate clock spanning all registers or they can be divided into
the 10 individual gates containing 16 clocks each.
The code supports both approaches.

Required properties:
- compatible : "rockchip,rk2928-gate-clk"
- reg : shall be the control register address(es) for the clock.
- #clock-cells : from common clock binding; shall be set to 1
- clock-output-names : the corresponding gate names that the clock controls
- clocks : should contain the parent clock for each individual gate,
  therefore the number of clocks elements should match the number of
  clock-output-names

Example using multiple gate clocks:

		clk_gates0: gate-clk@200000d0 {
			compatible = "rockchip,rk2928-gate-clk";
			reg = <0x200000d0 0x4>;
			clocks = <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>,
				 <&dummy>, <&dummy>;

			clock-output-names =
				"gate_core_periph", "gate_cpu_gpll",
				"gate_ddrphy", "gate_aclk_cpu",
				"gate_hclk_cpu", "gate_pclk_cpu",
				"gate_atclk_cpu", "gate_i2s0",
				"gate_i2s0_frac", "gate_i2s1",
				"gate_i2s1_frac", "gate_i2s2",
				"gate_i2s2_frac", "gate_spdif",
				"gate_spdif_frac", "gate_testclk";

			#clock-cells = <1>;
		};

		clk_gates1: gate-clk@200000d4 {
			compatible = "rockchip,rk2928-gate-clk";
			reg = <0x200000d4 0x4>;
			clocks = <&xin24m>, <&xin24m>,
				 <&xin24m>, <&dummy>,
				 <&dummy>, <&xin24m>,
				 <&xin24m>, <&dummy>,
				 <&xin24m>, <&dummy>,
				 <&xin24m>, <&dummy>,
				 <&xin24m>, <&dummy>,
				 <&xin24m>, <&dummy>;

			clock-output-names =
				"gate_timer0", "gate_timer1",
				"gate_timer2", "gate_jtag",
				"gate_aclk_lcdc1_src", "gate_otgphy0",
				"gate_otgphy1", "gate_ddr_gpll",
				"gate_uart0", "gate_frac_uart0",
				"gate_uart1", "gate_frac_uart1",
				"gate_uart2", "gate_frac_uart2",
				"gate_uart3", "gate_frac_uart3";

			#clock-cells = <1>;
		};