NVIDIA Tegra20/Tegra30 SLINK controller.

Required properties:
- compatible : should be "nvidia,tegra20-slink", "nvidia,tegra30-slink".
- reg: Should contain SLINK registers location and length.
- interrupts: Should contain SLINK interrupts.
- nvidia,dma-request-selector : The Tegra DMA controller's phandle and
  request selector for this SLINK controller.

Recommended properties:
- spi-max-frequency: Definition as per
                     Documentation/devicetree/bindings/spi/spi-bus.txt

Example:

spi@7000d600 {
	compatible = "nvidia,tegra20-slink";
	reg = <0x7000d600 0x200>;
	interrupts = <0 82 0x04>;
	nvidia,dma-request-selector = <&apbdma 16>;
	spi-max-frequency = <25000000>;
	#address-cells = <1>;
	#size-cells = <0>;
	status = "disabled";
};

