amd64_edac: add debugging/testing code

This is for dumping different registers and testing the address mapping
logic using the ECC syndromes.

Borislav:

- split sysfs attrs per file
- use more conform names for the sysfs attrs
- fix function return value patterns
- cleanup/fix comments
- cleanup debug calls

Reviewed-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>