ST-Ericsson COH 901 318 DMA Controller

This is a DMA controller which has begun as a fork of the
ARM PL08x PrimeCell VHDL code.

Required properties:
- compatible: should be "stericsson,coh901318"
- reg: register locations and length
- interrupts: the single DMA IRQ
- #dma-cells: must be set to <1>, as the channels on the
  COH 901 318 are simple and identified by a single number
- dma-channels: the number of DMA channels handled

Example:

dmac: dma-controller@c00020000 {
	compatible = "stericsson,coh901318";
	reg = <0xc0020000 0x1000>;
	interrupt-parent = <&vica>;
	interrupts = <2>;
	#dma-cells = <1>;
	dma-channels = <40>;
};

Consumers example:

uart0: serial@c0013000 {
	compatible = "...";
	(...)
	dmas = <&dmac 17 &dmac 18>;
	dma-names = "tx", "rx";
};
