JFFS2: don't fail on bitflips in OOB

JFFS2: don't fail on bitflips in OOB

commit 74d83beaa229aac7d126ac1ed9414658ff1a89d2 upstream.

JFFS2 was designed without thought for OOB bitflips, it seems, but they
can occur and will be reported to JFFS2 via mtd_read_oob()[1]. We don't
want to fail on these transactions, since the data was corrected.

[1] Few drivers report bitflips for OOB-only transactions. With such
    drivers, this patch should have no effect.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>