net/mlx5e: Allow legacy vf ndos only if in legacy mode

We will re-use the native NIC port net device instance for the Uplink
representor. Several VF ndo ops are not relevant in switchdev mode.
Disallow them when eswitch mode is not legacy as a preparation.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>