EDAC: Add DDR4 flag

Make EDAC aware of DDR4/RDDR4 mem types.

Signed-off-by: Jim Snow <jim.m.snow@intel.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/1449136134-23706-2-git-send-email-hubert.chrzaniuk@intel.com
[ Rebase to 4.4-rc3. ]
Signed-off-by: Hubert Chrzaniuk <hubert.chrzaniuk@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>