net/mlx4_core: fix typo in mlx4_set_vf_mac

fix typo in mlx4_set_vf_mac

Acked-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Carol L Soto <clsoto@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>