edac: move EDAC PCI definitions to drivers/edac/edac_pci.h

The edac_core.h header contain data structures and function
definitions for the 3 parts of EDAC: MC, PCI and device.

Let's move the PCI ones to a separate header file, as part
of a header reorganization.

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