MXC: mach-mx31_3ds: Add support for on board NAND Flash.

Since the using of Bad Block Table is not constantly a good behave
I had made it configurable.

Signed-off-by: Alberto Panizzo <maramaopercheseimorto@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>