de4x5/PCI: use list_for_each_entry() for bus->devices traversal

Replace open-coded list traversal with list_for_each_entry().

CC: Grant Grundler <grundler@parisc-linux.org>
CC: netdev@vger.kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>