PCI: always export pci_scan_single_device

This patch fixes the following build error with CONFIG_HOTPLUG=n:

  MODPOST 2137 modules
ERROR: "pci_scan_single_device" [drivers/edac/i82875p_edac.ko] undefined!

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Doug Thompson <norsk5@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>