devicetree:bindings: add devicetree bindings for Freescale AHCI

Binding for Freescale QorIQ AHCI SATA Controller

Required properties:

  - reg: Physical base address and size of the controller's register area.

  - compatible: Compatibility string. Must be 'fsl,<chip>-ahci', where

    chip could be ls1021a, ls2085a, ls1043a etc.

  - clocks: Input clock specifier. Refer to common clock bindings.

  - interrupts: Interrupt specifier. Refer to interrupt binding.

Optional properties:

  - dma-coherent: Enable ACHI coherency DMA operation.

  - reg-names: register area names when there are more then 1 regster area.

Examples:

	sata@3200000 {

		compatible = "fsl,ls1021a-ahci";

		reg = <0x0 0x3200000 0x0 0x10000>;

		interrupts = <GIC_SPI 101 IRQ_TYPE_LEVEL_HIGH>;

		clocks = <&platform_clk 1>;

		dma-coherent;

	};