[U-Boot] U-boot PPC405EX with DDR2 DIMM

[Steve Miller]

Just wanted to tell the group that I am abandoning using the SPD data on
PPC405EX.  As I stated earlier, I inherited this design from others.
As I dug deeper into the HW, I found that a X64 module was used on a
processor that only has a X32 wide bus.  Apparently, they could get
modules for less than 1/2 the DRAM cost as 50% of the memory is unused.
This is most likely why no one is currently using DIMMs on the 405EX.
There are no commercially available X32 DIMMs in DDR2.  

My thanks to  Stefan and others for their suggestions.    I believe this
design I am working on will be limited to only one DIMM type.
Therefore, I am just going to assign the parameters in the header file
for this board. 

---- Steve