be2net: Fix to prevent flooding of TX queue

Start/stop TX queue is controlled by TX queue "used" counter.
It is incremented while WRBs are posted to TX queue and
decremented when TX completions are received. This counter was
getting decremented before HW is informed about processing of TX
completions. As used counter is decremented, transmit function
posts new WRBs and creates completion queue full scenario in HW.

Signed-off-by: Padmanabh Ratnakar <padmanabh.ratnakar@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>