mtd: nand: Add MPC5121 NAND Flash Controller driver

Adds NAND Flash Controller driver for MPC5121 Revision 2.
All device features, except hardware ECC and power management,
are supported.

Signed-off-by: Piotr Ziecik <kosmo@semihalf.com>
Signed-off-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>