PCI: PM: Fix ordering of operations in pci_back_from_sleep()

The ordering of operations in pci_back_from_sleep() is incorrect,
because the device may be in D3cold when it runs and pci_enable_wake()
needs to access the device's configuration space which cannot be
done in D3cold.

Fix this by calling pci_set_power_state() to put the device into D0
before calling pci_enable_wake() for it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>