PCI: vmd: Assign vector zero to all bridges

We don't want slower IRQ handlers impacting faster devices that happen to
be assigned the same VMD interrupt vector. The driver was trying to
separate such devices by checking if MSI-X wasn't used, but really we just
don't want endpoint devices to share with bridges. Most bridges may use MSI
currently, so that criteria happened to work, but newer ones may use MSI-X,
so this patch explicitly checks the device type when choosing a vector.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>