Initialize itolb spinlock.

Fixes: 5262912e ("vdpa/mlx5: Add support for control VQ and MAC setting")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Message-Id: <20230206122016.1149373-1-elic@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>