Broadcom BCM2835 SPI0 controller

The BCM2835 contains two forms of SPI master controller, one known simply as
SPI0, and the other known as the "Universal SPI Master"; part of the
auxiliary block. This binding applies to the SPI0 controller.

Required properties:
- compatible: Should be "brcm,bcm2835-spi".
- reg: Should contain register location and length.
- interrupts: Should contain interrupt.
- clocks: The clock feeding the SPI controller.

Example:

spi@20204000 {
	compatible = "brcm,bcm2835-spi";
	reg = <0x7e204000 0x1000>;
	interrupts = <2 22>;
	clocks = <&clk_spi>;
	#address-cells = <1>;
	#size-cells = <0>;
};