vdpa/mlx5: Add error code for suspend/resume VQ

Instead of blindly calling suspend/resume_vqs(), make then return error
codes.

To keep compatibility, keep suspending or resuming VQs on error and
return the last error code. The assumption here is that the error code
would be the same.

Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Message-Id: <20240626-stage-vdpa-vq-precreate-v2-17-560c491078df@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>