pktgen: fix xmit test for BQL enabled devices

Similarly as in commit 8e2f1a63 ("packet: fix packet_direct_xmit
for BQL enabled drivers"), we test for __QUEUE_STATE_STACK_XOFF bit
in pktgen's xmit, which would not fully fill the device's TX ring for
BQL drivers that use netdev_tx_sent_queue(). Fix is to use, similarly
as we do in packet sockets, netif_xmit_frozen_or_drv_stopped() test.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/pktgen.c

@@ -3340,7 +3340,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 
 	__netif_tx_lock_bh(txq);
 
-	if (unlikely(netif_xmit_frozen_or_stopped(txq))) {
+	if (unlikely(netif_xmit_frozen_or_drv_stopped(txq))) {
 		ret = NETDEV_TX_BUSY;
 		pkt_dev->last_ok = 0;
 		goto unlock;