RFC: Booting from NAND for mini2440 platform

[Juergen Beisert]

This patch series brings in NAND boot support for the mini24040 platform and
also does some cleanup (and also fixes some typos).

Testes are welcome, as I only have a mini2440 board with HY57V561620 SDRAM
devices. I added some documentation (thanks to Marek for info how it works
with DFU) about the board itself and how to bring in barebox. Hope it helps
others to enjoy barebox on mini2440.

Regards,
Juergen