toradex: colibri_vf: fix memory initialization

Commit 3f353cec ("vf610: refactor DDRMC code") changed on-die
termination (ODT) values from 120 Ohm to 60 Ohm and enabled a static
read/write leveling which has not been tested with this board. This
commit reverts both changes and makes sure that memory gets
initialized as it has been done before the mentioned commit.

Fixes: 3f353cec ("vf610: refactor DDRMC code")
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Acked-by: Max Krummenacher <max.krummenacher@toradex.com>