amd64_edac: Cleanup error injection code

Invert kstrtoul return value testing and win one indentation level.
Also, shorten up macro names so that the lines can fit into 80 cols. No
functional change.

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

diff --cc drivers/edac/amd64_edac.h
Simple merge

diff --cc drivers/edac/amd64_edac_inj.c
Simple merge