Currently mtdconcat is broken for NAND. An attemtpt to create
JFFS2 filesystem on concatenation of several NAND devices fails
with OOB write errors. This patch fixes that problem.

Signed-off-by: Felix Radensky <felix@embedded-sol.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>