powerpc/eeh: Add bdfn field to eeh_dev

Preparation for removing pci_dn from the powernv EEH code. The only
thing we really use pci_dn for is to get the bdfn of the device for
config space accesses, so adding that information to eeh_dev reduces
the need to carry around the pci_dn.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
[SB: Re-wrapped commit message, fixed whitespace damage.]
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e458eb69a1f591d8a120782f23a8506b15d3c654.1565930772.git.sbobroff@linux.ibm.com