PCI / PM: Disable wakeup during shutdown for devices not enabled to wake up

If a PCI device is enabled to generate wakeup signals (PME) when put
into a low-power state by runtime PM, it will be still enabled to
generate those signals after the system shutdown, unless its driver's
.shutdown() callback takes care of the wakeup signals generation
setting.  Moreover, there are devices that are not enabled to wake
up the system and that are configured by runtime PM to generate
wakeup signals so that (runtime) remote wakeup works with them.
Those devices should be reconfigured during system shutdown so that
they don't generate wakeup signals, but at least some drivers don't
do that.  However, that very well may be done by the PCI core so
that drivers don't have to worry about it.  For this reason, modify
pci_device_shutdown() to disable the generation of wakeup events for
devices not supposed to wake up the system.

References: https://bugzilla.kernel.org/show_bug.cgi?id=37952


Reported-and-tested-by: Kamil Iskra <kamil.54002@iskra.name>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>