net/mlx5: Introduce access functions to modify/query vport vlans

Those functions are needed to notify the upcoming L2 table and SR-IOV
E-Switch(FDB) manager(PF), of the NIC vport (vf) vlan table changes.

preperation for ethernet sriov and l2 table management.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>