ATMEL: fix nand ecc support

So we can now choose for the board the ecc mode (ecc soft, soft bch, no ecc
and hardware).

Set ecc mode in the boards to soft as currently in the driver.

Move platform data to a common header
include/linux/platform_data/atmel_nand.h

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Acked-by: David Woodhouse <dwmw2@infradead.org>

arch/arm/mach-at91/board-snapper9260.c

@@ -110,6 +110,7 @@ static struct atmel_nand_data __initdata snapper9260_nand_data = {
 	.bus_width_16	= 0,
 	.enable_pin	= -EINVAL,
 	.det_pin	= -EINVAL,
+	.ecc_mode	= NAND_ECC_SOFT,
 };
 
 static struct sam9_smc_config __initdata snapper9260_nand_smc_config = {