[coreboot] [PATCH] Athlon64 K8 fixes

[Robert Millan]

Hi,

My Athlon64 / K8 socket 939 setup needed the following adjustments to fix
memory read/write errors.  Thanks to Rudolf for hinting on which bits I
should check for.  Details:

- bit 9, mandated by spec to always be set on sodimm or socket 939 dual
   dimm.

- bit 28, enable 2T timing.  no idea why, but I get memory errors without
   it.

- bit 29, upper chip select.  mandated by spec on socket 939.

My patch also adds missing descriptions, based on the ones from the spec
(http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/2609...)