Calxeda DDR memory controller

Properties:
- compatible : Should be "calxeda,hb-ddr-ctrl"
- reg : Address and size for DDR controller registers.
- interrupts : Interrupt for DDR controller.

Example:

	memory-controller@fff00000 {
		compatible = "calxeda,hb-ddr-ctrl";
		reg = <0xfff00000 0x1000>;
		interrupts = <0 91 4>;
	};
