Atmel AT25 eeprom

Required properties:
- compatible : "atmel,at25".
- reg : chip select number
- spi-max-frequency : max spi frequency to use

- at25,byte-len : total eeprom size in bytes
- at25,addr-mode : addr-mode flags, as defined in include/linux/spi/eeprom.h
- at25,page-size : size of the eeprom page

Examples:
at25@0 {
	compatible = "atmel,at25";
	reg = <0>
	spi-max-frequency = <5000000>;

	at25,byte-len = <0x8000>;
	at25,addr-mode = <2>;
	at25,page-size = <64>;
};