mtd: return badblockbits back

In commit c7b28e25 the initialization of
the backblockbits was accidentally removed. This patch returns it back,
because otherwise some NAND drivers are broken.

This problem was reported by "Saxena, Parth <parth.saxena@ti.com>" here:
http://lists.infradead.org/pipermail/linux-mtd/2011-April/035221.html



Reported-by: Saxena, Parth <parth.saxena@ti.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Tested-by: Saxena, Parth <parth.saxena@ti.com>
Acked-by: Saxena, Parth <parth.saxena@ti.com>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Cc: stable@kernel.org [2.6.36+]
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>