MFC r319414:
Allow communication between functions on the same host when using the
mlx4en(4) driver in SRIOV mode.

Place a copy of the destination MAC address in the send WQE only under
SRIOV/eSwitch configuration or when the device is in selftest. This
allows communication between functions on the same host.

PR: 216493
Approved by: re (kib)
Sponsored by: Mellanox Technologies