mtd: Blackfin NFC: fix badblock location with BootROM OOB

The bbt structure isn't actually used, just the badblockpos.  This lets
the driver correctly handle badblocks with the different OOB layout with
certain sized flashes.  Previously, the blocks would all be reported as
bad and be completely unusable.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>