sb_edac: look harder for DDRIO on Haswell systems

In case the memory banks are populated so the first channel isn't used, the
DDRIO PCI device won't be visible and it won't be possible to determine the
memory type.

Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>