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>
diff --git a/arch/arm/mach-at91/board-stamp9g20.c b/arch/arm/mach-at91/board-stamp9g20.c
index 72eb3b4..7640049 100644
--- a/arch/arm/mach-at91/board-stamp9g20.c
+++ b/arch/arm/mach-at91/board-stamp9g20.c
@@ -86,6 +86,7 @@
 	.enable_pin	= AT91_PIN_PC14,
 	.bus_width_16	= 0,
 	.det_pin	= -EINVAL,
+	.ecc_mode	= NAND_ECC_SOFT,
 };
 
 static struct sam9_smc_config __initdata nand_smc_config = {