PCI: Make pci_get_host_bridge_device(), pci_put_host_bridge_device() private

PCI: Make pci_get_host_bridge_device(), pci_put_host_bridge_device() private

These interfaces:

  struct device *pci_get_host_bridge_device(struct pci_dev *dev);
  void pci_put_host_bridge_device(struct device *dev);

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/20190724233848.73327-4-skunberg.kelsey@gmail.com
Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>