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.
- clocks : Must contain one entry, for the module clock.
  See ../clocks/clock-bindings.txt for details.
- resets : Must contain an entry for each entry in reset-names.
  See ../reset/reset.txt for details.
- reset-names : Must include the following entries:
  - spi
- dmas : Must contain an entry for each entry in clock-names.
  See ../dma/dma.txt for details.
- dma-names : Must include the following entries:
  - rx
  - tx

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

Example:

spi@7000c380 {
	compatible = "nvidia,tegra20-sflash";
	reg = <0x7000c380 0x80>;
	interrupts = <0 39 0x04>;
	spi-max-frequency = <25000000>;
	#address-cells = <1>;
	#size-cells = <0>;
	clocks = <&tegra_car 43>;
	resets = <&tegra_car 43>;
	reset-names = "spi";
	dmas = <&apbdma 11>, <&apbdma 11>;
	dma-names = "rx", "tx";
};
