cxgb3: Set the rxq

Set the rxq# for LRO when processing the last fragment of a
frame. This helps in fast txq selection for routing workloads.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Acked-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>