amd64_edac: cleanup/complete NB MCE decoding

* don't dump info which mcheck already does
* update to newest BKDG
* mv amd64_process_error_info -> amd64_decode_nb_mce
* shorten error struct names
* remove redundant info ptr in amd64_process_error_info
* remove unused ErrorCodeExt[19:16] (MCx_STATUS) defines

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>