net/mlx4: Spoofcheck and zero MAC can't coexist

Spoofcheck can't be enabled if VF MAC is zero.
Vice versa, can't zero MAC if spoofcheck is on.

Fixes: 8f7ba3ca

 ('net/mlx4: Add set VF mac address support')
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>