pci: Additional search functions

In order to finish converting to pci_get_* interfaces we need to add a couple
of bits of missing functionaility

pci_get_bus_and_slot() provides the equivalent to pci_find_slot()
(pci_get_slot is already taken as a name for something similar but not the
same)

pci_get_device_reverse() is the equivalent of pci_find_device_reverse but
refcounting

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>