EDAC/amd64: Merge error injection sysfs facilities

Merge them into the main driver and put them inside an EDAC_DEBUG
ifdeffery to simplify the driver and have all debugging/injection stuff
behind a debug build-time switch.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Link: https://lkml.kernel.org/r/20201215110517.5215-2-bp@alien8.de