powerpc/mpc8349emds: Migrate from spd_sdram to unified DDR driver

Update MPC8349EMDS to use unified DDR driver instead of spd_sdram.c.
The unified driver can initialize data using DDR controller. No need to
use DMA if just to initialze for ECC.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>