[MTD] OneNAND: fix oob handling in recent oob patch

There are missing place in recent MTD oob patch

http://git.infradead.org/?p=mtd-2.6.git;a=commitdiff;h=7014568bad55c20b7ee4f439d78c9e875912d51f



Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>