EDAC, sb_edac: Fix missing break in switch

Add missing break statement in order to prevent the code from falling
through.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Cc: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20171016174029.GA19757@embeddedor.com


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