net/mlx4_core: Add security check / enforcement for flow steering rules set for VMs

Since VFs may be mapped to VMs which aren't trusted entities,  flow
steering rules attached through the wrapper on behalf of VFs must be
checked to make sure that their L2 specification relate to MAC address
assigned to that VF, and add L2 specification if its missing.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>