With 2k NAND flashes the data layout in memory is not what is
written on the flash device. This leads to the result that the
factory provided bad block markers are not recognized correctly.

To preserve the factory bad block information the i.MX NAND driver
will not scan for the bad blocks itself when there is no flash based
bbt available, because the mtd layer would do so based on wrong
information. Instead, a new command is introduced which allows to
manually create a flash bbt based on the correct information.

As this command is tightly coupled to mtd and the i.MX NAND driver
the command is placed under drivers/mtd/nand/ instead of commands/
where a command normally belongs to.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>