net/mlx5: E-switch, Consider maximum vf vports for steering init

When eswitch is enabled, VFs might not be enabled. Hence, consider
maximum number of VFs.
This further closes the gap between handling VF vports between ECPF and
PF.

Fixes: ea2128fd

 ("net/mlx5: E-switch, Reduce dependency on num_vfs during mode set")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>