Avoid executing set_vq_ready() if the device has been reset. In such
case, the features are cleared and cannot be used in conditional
statements. Such reference happens is the function ctrl_vq_idx().

Fixes: 52893733 ("vdpa/mlx5: Add multiqueue support")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20210909063738.46970-1-elic@nvidia.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>