net: netdev_queue: netdev_txq_completed_mb(): fix wake condition

netif_txq_try_stop() uses "get_desc >= start_thrs" as the check for
the call to netif_tx_start_queue().

Use ">=" i netdev_txq_completed_mb(), too.

Fixes: c91c46de

 ("net: provide macros for commonly copied lockless queue stop/wake code")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>