net/mlx4: && vs & typo

Bitwise & was obviously intended here.

Fixes: 745d8ae4

 ("net/mlx4: Spoofcheck and zero MAC can't coexist")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>