[MTD] OneNAND: return ecc error code only when 2-bit ecc occurs
we don't need to return ecc error when 1-bit ecc.
We only return error code when 2-bit ecc error
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
authored by Kyungmin Park and committed by Artem Bityutskiy b3c9f8bf a8de85d5