Allows the PF to enforce the VF's mac.
i.e., by using `ip link ... vf <x> mac <value>'.

While a MAC is forced, PF would prevent the VF from configuring any other
MAC.
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>