vfio: Make VFIOContainerBase poiner parameter const in VFIOIOMMUOps callbacks

vfio: Make VFIOContainerBase poiner parameter const in VFIOIOMMUOps callbacks

Some of the callbacks in VFIOIOMMUOps pass VFIOContainerBase poiner,
those callbacks only need read access to the sub object of VFIOContainerBase.
So make VFIOContainerBase, VFIOContainer and VFIOIOMMUFDContainer as const
in these callbacks.

Local functions called by those callbacks also need same changes to avoid
build error.

Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>