immediately from acpi_pci_link_route_interrupt() since we aren't going
to have a valid pci_link device to talk to try to route interrupts. This
fixes a page fault if you disable just pci_link. Note that trying to use
ACPI without pci_link is probably not advised however.
MFC after: 1 week
Tested by: Eugene Grosbein eugen at kuzbass dot ru