powerpc/85xx: Fix P2020DS booting

The following commit removed the code that set odt_rd_cfg and
odt_wr_cfg.  With out this code P2020DS board will not boot:

commit 712cf7ab
Author: York Sun <yorksun@freescale.com>
Date:   Mon Oct 3 09:19:53 2011 -0700

    powerpc/mpc8xxx: Merge entries in DDR speed table

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>