ppc4xx: Change DDR2 CL from 4 to 5 for intip

Some intip boards don't seem to run stable with CL4, datasheets suggest that
CL5 is the safe value.

Signed-off-by: Dirk Eibach <eibach@gdsys.de>
Signed-off-by: Stefan Roese <sr@denx.de>