net: thunderx: Enable CQE_RX desc's extension fields

Unlike 88xx, CQE_RX descriptor's tunnelling extension i.e CQE_RX2_S
is always enabled on 81xx/83xx and HW does insert these fields into
CQE_RX. As a result receive buffer addresses will now be present at
7th word of CQE_RX instead of 6th.

Enable CQE_RX2_S on 88xx pass 2.x as well.

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>