PCI: Make pci_set_of_node(), etc private

PCI: Make pci_set_of_node(), etc private

These interfaces:

  void pci_set_of_node(struct pci_dev *dev);
  void pci_release_of_node(struct pci_dev *dev);
  void pci_set_bus_of_node(struct pci_bus *bus);
  void pci_release_bus_of_node(struct pci_bus *bus);

are only used in drivers/pci/ and do not need to be seen by the rest of the
kernel.  Move them to drivers/pci/pci.h so they're private to the PCI
subsystem.

Link: https://lore.kernel.org/r/20190724233848.73327-12-skunberg.kelsey@gmail.com
Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>