nandflash: support for ubi.

This is a basic implementation to support for UBI.
There is no check for CRC headers, and there is no check about the
redundant table for volume records.

Those features will come up soon. Currently, this is an experimental
version and the code must remain light to feet into the first 128k of NAND
flash.

The UBI support let you boot a kernel image or a bootloader and make their
upgrade safer using spare volumes. Is spreads as well the wear on
almost all NAND flash memory (the first block must contains the bootstrap
binary).

Signed-off-by: Gaël PORTAY <gael.portay@gmail.com>
board: add ubi linux defconfig support.

Signed-off-by: Gaël PORTAY <gael.portay@gmail.com>
debug: add support for hexdump function.

Signed-off-by: Gaël PORTAY <gael.portay@gmail.com>
board: support for kizbox board.

Signed-off-by: Gaël PORTAY <gael.portay@gmail.com>