net/mlx5: E-Switch, Honor eswitch functions changed event cap

Whenever device supports eswitch functions changed event, honor
such device setting. Do not limit it to ECPF.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Vu Pham <vuhuong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>