[PATCH] Be careful about memory ordering in sungem driver

[PATCH] Be careful about memory ordering in sungem driver

Some barriers between setting up the DMA regions and writing the
descriptor addresses would be most useful.

I had some in my 2.4 version but they got lost someway, probably me not
properly merging with davem at this point.  The 970 is definitely more
agressive at re-ordering stores than previous CPUs...

Here is a patch adding some (probably too much, but better safe than
sorry).