cxgb4i: use set_wr_txq() to set tx queues

use cxgb4's set_wr_txq() for setting of the tx queue for a outgoing packet.
remove the similar function in cxgb4i.

Signed-off-by: Karen Xie <kxie@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>