vfio/mlx5: Check whether VF is migratable

Add a check whether VF is migratable. Only if VF is migratable, mark the
VFIO device as migration capable.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20230124144955.139901-2-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>