FLCTL NAND controller

Required properties:
- compatible : "renesas,shmobile-flctl-sh7372"
- reg : Address range of the FLCTL
- interrupts : flste IRQ number
- nand-bus-width : bus width to NAND chip

Optional properties:
- dmas: DMA specifier(s)
- dma-names: name for each DMA specifier. Valid names are
	     "data_tx", "data_rx", "ecc_tx", "ecc_rx"

The DMA fields are not used yet in the driver but are listed here for
completing the bindings.

The device tree may optionally contain sub-nodes describing partitions of the
address space. See mtd.yaml for more detail.

Example:

	flctl@e6a30000 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "renesas,shmobile-flctl-sh7372";
		reg = <0xe6a30000 0x100>;
		interrupts = <0x0d80>;

		nand-bus-width = <16>;

		dmas = <&dmac 1 /* data_tx */
			&dmac 2;> /* data_rx */
		dma-names = "data_tx", "data_rx";

		system@0 {
			label = "system";
			reg = <0x0 0x8000000>;
		};

		userdata@8000000 {
			label = "userdata";
			reg = <0x8000000 0x10000000>;
		};

		cache@18000000 {
			label = "cache";
			reg = <0x18000000 0x8000000>;
		};
	};