net/mlx5: MPFS, Allow adding the same MAC more than once

Remove the limitation preventing adding a vport's MAC address to the
Multi-Physical Function Switch (MPFS) more than once per E-switch, as
there is no difference in the MPFS if an address is being used by an
E-switch more than once.

This allows the E-switch to have multiple vports with the same MAC
address, allowing vports to be classified by VLAN id instead of by MAC
if desired.

Signed-off-by: Gavi Teitz <gavi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>