EDAC, sb_edac: Set fixed DIMM width on Xeon Knights Landing

Knights Landing does not come with register that could be used to fetch
DIMM width. However the value is fixed for this architecture so it can
be hardcoded.

Signed-off-by: Hubert Chrzaniuk <hubert.chrzaniuk@intel.com>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: lukasz.anaczkowski@intel.com
Link: http://lkml.kernel.org/r/1449840082-18673-1-git-send-email-hubert.chrzaniuk@intel.com


Signed-off-by: Borislav Petkov <bp@suse.de>