ifcvf: implement config interrupt in IFCVF

This commit implements config interrupt support
in IFC VF

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/1591352835-22441-6-git-send-email-lingshan.zhu@intel.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>