net/mlx5e: Avoid dealing with vport representors if not being e-switch manager

In smartnic env, the host (PF) driver might not be an e-switch
manager, hence the switchdev mode representors are running on
the embedded cpu (EC) and not at the host.

As such, we should avoid dealing with vport representors if
not being esw manager.

While here, make sure to disallow eswitch switchdev related
setups through devlink if we are not esw managers.

Fixes: cb67b832 ('net/mlx5e: Introduce SRIOV VF representors')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>