vfio/type1: Fix migration info capability ID

ID 1 is already used by the IOVA range capability, use ID 2.

Reported-by: Liu Yi L <yi.l.liu@intel.com>
Fixes: ad721705 ("vfio iommu: Add migration capability to report supported features")
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>