i7core_edac: Fix refcount error at PCI devices

Probably due to a bug or some testing logic at PCI level, device
refcount for <bus>:00.0 device is decremented at the end of the
pci_get_device, made by i7core_get_all_devices(). The fact is that
the first versions of the driver relied on those devices to probe
for Nehalem, but the current versions don't use it at all.

So, let's just remove those devices from the driver, making it simpler
and fixing the bug.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>