arm: omap: Fix switching back to nandecc sw.

arm: omap: Fix switching back to nandecc sw.

Orjan Friberg wrote at [1]:

"For the beagleboard, ecc.size is not explicitly set when doing 'nandecc
sw'. If it's not set for the NAND_ECC_SOFT case in nand_scan_tail, it's
set to 256 bytes.

When doing 'nandecc hw', ecc.size is set to 512 bytes. Hence, when
changing back to 'nandecc sw' ecc.size remains at 512 bytes and suddenly
the format has changed."

No patch has been submitted and the issue was still present. This patch
adds the mentioned solution. Tested on a tam3517 board.

[1] http://lists.denx.de/pipermail/u-boot/2012-February/119002.html

cc: Orjan Friberg <of@flatfrog.com>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>
Acked-by: Nikita Kiryanov <nikita@compulab.co.il>
Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>