NVIDIA Tegra20 SFLASH controller.

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

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

Example:

spi@7000d600 {
	compatible = "nvidia,tegra20-sflash";
	reg = <0x7000c380 0x80>;
	interrupts = <0 39 0x04>;
	nvidia,dma-request-selector = <&apbdma 16>;
	spi-max-frequency = <25000000>;
	#address-cells = <1>;
	#size-cells = <0>;
	status = "disabled";
};

