PCI PM: Export pci_pme_active to drivers

Export pci_pme_active() to drivers, so that they can clear the
PME_status bit and disable PME# for their devices without involving
ACPI.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>