Binding for Broadcom BCM6348/BCM6358 SPI controller

Required properties:
- compatible: must contain one of "brcm,bcm6348-spi", "brcm,bcm6358-spi".
- reg: Base address and size of the controllers memory area.
- interrupts: Interrupt for the SPI block.
- clocks: phandle of the SPI clock.
- clock-names: has to be "spi".
- #address-cells: <1>, as required by generic SPI binding.
- #size-cells: <0>, also as required by generic SPI binding.

Optional properties:
- num-cs: some controllers have less than 8 cs signals. Defaults to 8
  if absent.

Child nodes as per the generic SPI binding.

Example:

	spi@10000800 {
		compatible = "brcm,bcm6368-spi", "brcm,bcm6358-spi";
		reg = <0x10000800 0x70c>;

		interrupts = <1>;

		clocks = <&clkctl 9>;
		clock-names = "spi";

		num-cs = <5>;

		#address-cells = <1>;
		#size-cells = <0>;
	};
