EDAC, sb_edac: Assign EDAC memory controller per h/w controller

Tony pointed out: "currently the driver pretends there is one big
8-channel memory controller per socket instead of 2 4-channel
controllers. This is fine with all memory controller populated with
symmetrical DIMM configurations, but runs into difficulties on
asymmetrical setups".

Restructure the driver to assign an EDAC memory controller to each real
h/w memory controller to resolve the issue.

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170523000731.87793-1-qiuxu.zhuo@intel.com
[ Break some lines at convenient points. ]
Signed-off-by: Borislav Petkov <bp@suse.de>