PCI: PM: Simplify bus-level hibernation callbacks

After a previous change causing all runtime-suspended PCI devices
to be resumed before creating a snapshot image of memory during
hibernation, it is not necessary to worry about the case in which
them might be left in runtime-suspend any more, so get rid of the
code related to that from bus-level PCI hibernation callbacks.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>