Switch to pci_get_bus_and_slot because some x86 systems seem to be
handing us a device with dev->bus = NULL. Also don't apply the isa fixup
to revision C6 and later of the chip.

Really we need to work out wtf is handing us pdev->bus = NULL, but firstly
and more importantly we need the drivers working.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>