This patch adds the registration/unregistration of an
irq_bypass_producer for MSI/MSIx on vfio pci devices.
Acked-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NFeng Wu <feng.wu@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>