net/mlx5: Prevent setting multicast macs for VFs

Need to check that VF mac address entered by the admin user is either
zero or unicast mac.
Multicast mac addresses are prohibited.

Fixes: 77256579 ('net/mlx5: E-Switch, Introduce Vport administration functions')
Signed-off-by: Mohamad Haj Yahia <mohamad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>