Binding for Broadcom BCM6328 High Speed SPI controller

Required properties:
- compatible: must contain of "brcm,bcm6328-hsspi".
- reg: Base address and size of the controllers memory area.
- interrupts: Interrupt for the SPI block.
- clocks: phandles of the SPI clock and the PLL clock.
- clock-names: must be "hsspi", "pll".
- #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@10001000 {
		compatible = "brcm,bcm6328-hsspi";
		reg = <0x10001000 0x600>;

		interrupts = <29>;

		clocks = <&clkctl 9>, <&hsspi_pll>;
		clock-names = "hsspi", "pll";

		num-cs = <2>;

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