dt-bindings: dma: Add binding for jz4780-dma

* Ingenic JZ4780 DMA Controller

Required properties:

- compatible: Should be "ingenic,jz4780-dma"

- reg: Should contain the DMA controller registers location and length.

- interrupts: Should contain the interrupt specifier of the DMA controller.

- interrupt-parent: Should be the phandle of the interrupt controller that

- clocks: Should contain a clock specifier for the JZ4780 PDMA clock.

- #dma-cells: Must be <2>. Number of integer cells in the dmas property of

  DMA clients (see below).

Optional properties:

- ingenic,reserved-channels: Bitmask of channels to reserve for devices that

  need a specific channel. These channels will only be assigned when explicitly

  requested by a client. The primary use for this is channels 0 and 1, which

  can be configured to have special behaviour for NAND/BCH when using

  programmable firmware.

Example:

dma: dma@13420000 {

	compatible = "ingenic,jz4780-dma";

	reg = <0x13420000 0x10000>;

	interrupt-parent = <&intc>;

	interrupts = <10>;

	clocks = <&cgu JZ4780_CLK_PDMA>;

	#dma-cells = <2>;

	ingenic,reserved-channels = <0x3>;

};

DMA clients must use the format described in dma.txt, giving a phandle to the

DMA controller plus the following 2 integer cells:

1. Request type: The DMA request type for transfers to/from the device on

   the allocated channel, as defined in the SoC documentation.

2. Channel: If set to 0xffffffff, any available channel will be allocated for

   the client. Otherwise, the exact channel specified will be used. The channel

   should be reserved on the DMA controller using the ingenic,reserved-channels

   property.

Example:

uart0: serial@10030000 {

	...

	dmas = <&dma 0x14 0xffffffff

		&dma 0x15 0xffffffff>;

	dma-names = "tx", "rx";

	...

};