EDAC, amd64_edac: Drop pci_register_driver() use

- remove homegrown instances counting.
- take F3 PCI device from amd_nb caching instead of F2 which was used with the
PCI core.

With those changes, the driver doesn't need to register a PCI driver and
relies on the northbridges caching which we do anyway on AMD.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Yazen Ghannam <yazen.ghannam@amd.com>