PCI/PM: Propagate wake-up enable for PCIe devices too

Having read the PM part of the PCIe 2.0 specification more carefully
I think that it was a mistake to restrict the wake-up enable
propagation to non-PCIe devices, because if we do not request
control of the root ports' PME registers via OSC, PCIe PME is
supposed to be handled by the platform, just like the non-PCIe PME.
Even if we do that, the wake-up propagation is done to allow the
devices to wake up the system from sleep states which involves the
platform anyway, so it won't hurt.

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