Documentation: Add documentation for the APM X-Gene SoC EDAC DTS binding

Add documentation for the APM X-Gene SoC EDAC DTS binding.

Signed-off-by: Loc Ho <lho@apm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: devicetree@vger.kernel.org
Cc: dougthompson@xmission.com
Cc: ijc+devicetree@hellion.org.uk
Cc: jcm@redhat.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: mark.rutland@arm.com
Cc: mchehab@osg.samsung.com
Cc: patches@apm.com
Cc: robh+dt@kernel.org
Link: http://lkml.kernel.org/r/1432337580-3750-4-git-send-email-lho@apm.com


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