net: thunderx: Wakeup TXQ only if CQE_TX are processed

Previously TXQ is wakedup whenever napi is executed
and irrespective of if any CQE_TX are processed or not.
Added 'txq_stop' and 'txq_wake' counters to aid in debugging
if there are any future issues.

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