PCI: Rename pci_release_bus_bridge_dev() to pci_release_host_bridge_dev()

This renames pci_release_bus_bridge_dev() to pci_release_host_bridge_dev()
and moves it next to pci_alloc_host_bridge().  No functional change.

[bhelgaas: split rename & move out of create/destroy symmetry patch]
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>