arm/km: fix memory settings

On kmcoge5un we faced some serious problems with the memory during
temperature tests. Reason was that we overwrite some registers for
memory settings which have to leave untouched. These where registers
0x20148 , 0x2014c and 0x20154.
So writing these registers is prohibited and this patch removes them
from all km related config files. Even if the problem was only
seen on kmcoge5un.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>