ppc4xx: Adapt Canyonlands fixed DDR2 setup to new DIMM module

This patch changes the Canyonlands/Glacier fixed DDR2 controller setup
used for NAND booting to match the values needed for the new 512MB
DIMM modules shipped with the productions boards:

Crucial: CT6464AC667.8FB

Signed-off-by: Stefan Roese <sr@denx.de>