[PATCH] NAND: fix remaining OOB length calculation

In nand_read_page_syndrome/nand_write_page_syndrome the calculation of
the remaining oob length which is not used by the prepad/ecc/postpad
areas is wrong.

Signed-off-by: Vitaly Wool <vwool@ru.mvista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>