PCIe ASPM: use pci_is_pcie()

Change for PCIe ASPM driver to use pci_is_pcie() instead of checking
pci_dev->is_pcie.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>