Use pci_is_pcie() instead of looking at obsolete is_pcie field in
struct pci_dev.

CC: Huang Ying <ying.huang@intel.com>
CC: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>