Adding one property for intel-iommu devices to specify whether we should
support interrupt remapping. By default, IR is disabled. To enable it,
we should use (take Intel IOMMU as example):
-device intel_iommu,intremap=on
This property can be shared by Intel and future AMD IOMMUs.
Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>