Atmel NAND flash

Required properties:
- compatible : "atmel,at91rm9200-nand".
- reg : should specify localbus address and size used for the chip,
	and if availlable the ECC.
- atmel,nand-addr-offset : offset for the address latch.
- atmel,nand-cmd-offset : offset for the command latch.
- #address-cells, #size-cells : Must be present if the device has sub-nodes
  representing partitions.

- gpios : specifies the gpio pins to control the NAND device. detect is an
  optional gpio and may be set to 0 if not present.

Optional properties:
- nand-ecc-mode : String, operation mode of the NAND ecc mode, soft by default.
  Supported values are: "none", "soft", "hw", "hw_syndrome", "hw_oob_first",
  "soft_bch".
- nand-bus-width : 8 or 16 bus width if not present 8
- nand-on-flash-bbt: boolean to enable on flash bbt option if not present false

Examples:
nand0: nand@40000000,0 {
	compatible = "atmel,at91rm9200-nand";
	#address-cells = <1>;
	#size-cells = <1>;
	reg = <0x40000000 0x10000000
	       0xffffe800 0x200
	      >;
	atmel,nand-addr-offset = <21>;
	atmel,nand-cmd-offset = <22>;
	nand-on-flash-bbt;
	nand-ecc-mode = "soft";
	gpios = <&pioC 13 0
		 &pioC 14 0
		 0
		>;
	partition@0 {
		...
	};
};
