x86/PCI/VMD: Use untracked irq handler

x86/PCI/VMD: Use untracked irq handler

There is no way to know which device in a VMD triggered an interrupt
without invoking every registered driver's actions. This uses the
untracked irq handler so that a less used device does not trigger
spurious interrupt.

We have been previously recommending users to enable "noirqdebug", but do
not want to force a system setting just to keep this domain functional.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Jon Derrick <jonathan.derrick@intel.com>
Link: http://lkml.kernel.org/r/1466200821-29159-2-git-send-email-keith.busch@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>