powerpc/eeh: Remove unnecessary config_addr from eeh_dev

The eeh_dev struct hold a config space address of an associated node
and the very same address is also stored in the pci_dn struct which
is always present during the eeh_dev lifetime.

This uses bus:devfn directly from pci_dn instead of cached and packed
config_addr.

Since config_addr is made from device's bus:dev.fn, there is no point
in keeping it in the debugfs either so remove that too.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>