EDAC: move MCE error descriptions to EDAC core

This is in preparation of adding AMD-specific MCE decoding functionality
to the EDAC core. The error decoding macros originate from the AMD64
EDAC driver albeit in a simplified and cleaned up version here.

While at it, add macros to generate the error description strings and
use them in the error type decoders directly which removes a bunch of
code and makes the decoding functions much more readable. Also, fix
strings and shorten macro names.

Remove superfluous htlink_msgs.

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