Flash device on Intel IXP4xx SoC

This flash is regular CFI compatible (Intel or AMD extended) flash chips with
specific big-endian or mixed-endian memory access pattern.

Required properties:
- compatible : must be "intel,ixp4xx-flash", "cfi-flash";
- reg : memory address for the flash chip
- bank-width : width in bytes of flash interface, should be <2>

For the rest of the properties, see mtd-physmap.txt.

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

Example:

flash@50000000 {
	compatible = "intel,ixp4xx-flash", "cfi-flash";
	reg = <0x50000000 0x01000000>;
	bank-width = <2>;
};