PCI: limit pci_get_bus_and_slot to domain 0

Limit pci_get_bus_and_slot() to domain (segment) 0 since domain is not
specified in the function call and defaulting to domain 0 is the only
reasonable thing to do (rather than returning a device from some other
unknown domain).

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>