ionic: Check stop no restart

If there is a lot of transmit traffic the driver can get into a
situation that the device is starved due to the doorbell never
being rung. This can happen if xmit_more is set constantly
and __netdev_tx_sent_queue() keeps returning false. Fix this
by checking if the queue needs to be stopped right before
calling __netdev_tx_sent_queue(). Use MAX_SKB_FRAGS + 1 as the
stop condition because that's the maximum number of frags
supported for non-TSO transmit.

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>