net/mlx5: DR, Fix querying eswitch manager vport for ECPF

On BlueField the E-Switch manager is the ECPF (vport 0xFFFE), but when
querying capabilities of ECPF eswitch manager, need to query vport 0
with other_vport = 0.

Fixes: 9091b821

 ("net/mlx5: DR, Handle eswitch manager and uplink vports separately")
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>