EDAC: Move Doug Thompson to CREDITS

Doug hasn't been active as a maintainer for a long time now. Move him to
CREDITS.

Thanks for all the hard work, Doug!

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Doug Thompson <norsk5@yahoo.com>
Cc: Doug Thompson <dougthompson@xmission.com>