mtd: nand: make MTD_OOB_PLACE work correctly.

MTD_OOB_PLACE is supposed to read/write the raw oob data similiar to the
MTD_OOB_RAW however due to a bug, currently it is not possible to read
more data that is specified by the oob 'free' regions.

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>