[MTD] [NAND] Hardware ECC controller on at91sam9263 / at91sam9260

This is a patch to use the hardware ECC controller of
the AT91SAM9260 and AT91SAM9263 for the AT91 nand.
On AT91 NAND, there's now a choice between ECC soft,
ECC hard or no ECC (for debug).

It has been tested on AT91SAM9263 with 8 bits large
and small page NAND.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>