mtd: Add bad block table overrides to Davinci NAND driver

The existing NAND infrastructure allows the default main and
mirror bad block tables to be overridden in nand_default_bbt().
However, the davinci_nand driver does not support this.  Add
that support by adding fields to the davinci driver's platform
data so platform code can pass in their own bbt's and make the
davinci_nand driver honor them.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
CC: Sudhakar Rajashekhara <sudhakar.raj@ti.com>

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>