net/mlx5e: Only support tx/rx pause setting for port owner

Only support changing tx/rx pause frame setting if the net device
is the vport group manager.

Fixes: 3c2d18ef ("net/mlx5e: Support ethtool get/set_pauseparam")
Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>