ACPI: make acpi_pci_bind() static

acpi_pci_root_add() explicitly assigns device->ops.bind, and later
calls acpi_pci_bind_root(), which also does the same thing.

We don't need to repeat ourselves; removing the explicit assignment
allows us to make acpi_pci_bind() static.

Signed-off-by: Alex Chiang <achiang@hp.com>
Acked-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>