net/mlx4_en: Fix bridged vSwitch configuration for non SRIOV mode

net/mlx4_en: Fix bridged vSwitch configuration for non SRIOV mode

Commit da24e3d6e915 "mlx4_en: Allow communication between functions on
same host" introduced a regression under which a bridge acting as vSwitch
whose uplink is an mlx4 Ethernet device become non-operative in native
(non sriov) mode. This happens since broadcast ARP requests sent by VMs
were loopback-ed by the HW and hence the bridge learned VM source MACs
on both the VM and the uplink ports.

The fix is to place the DMAC in the send WQE only under SRIOV/eSwitch
configuration or when the device is in selftest.

Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>