ionic: Clean up BQL logic

The driver currently calls netdev_tx_completed_queue() for every
Tx completion. However, this API is only meant to be called once
per NAPI if any Tx work is done.  Make the necessary changes to
support calling netdev_tx_completed_queue() only once per NAPI.

Also, use the __netdev_tx_sent_queue() API, which supports the
xmit_more functionality.

Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>