drivers: ddr: imx Workaround for i.MX8M DDRPHY rank to rank issue

Add logic to automatically update umctl2's setting based
on phy training CDD value for rank to rank space issue

Acked-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Oliver Chen <Oliver.Chen@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
[Backport to v2020.01-ktn]
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>