AMD Fam15tn boards: Document lane ID mapping from BKDG

To make it easier to fill in the values, place the table
from the BIOS and Kernel Developer’s Guide (BKDG) [1]
as a comment.

[1] http://www.coreboot.org/Datasheets#AMD_Fam15

Change-Id: I218f76e9fa2dc88d47af51ea6c062e315afb0000
Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/3221
Tested-by: build bot (Jenkins)
3 files changed