Calxeda DDR memory controller

Properties:
- compatible : Should be:
  - "calxeda,hb-ddr-ctrl" for ECX-1000
  - "calxeda,ecx-2000-ddr-ctrl" for ECX-2000
- 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>;
	};
