net: declare new net_device priv_flag IFF_NO_QUEUE

This private net_device flag can be set by drivers to inform that a
device runs fine without a qdisc attached. This was formerly done by
setting tx_queue_len to zero.
Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1262,6 +1262,7 @@ struct net_device_ops {
  * @IFF_LIVE_ADDR_CHANGE: device supports hardware address
  *	change when it's running
  * @IFF_MACVLAN: Macvlan device
+ * @IFF_NO_QUEUE: device can run without qdisc attached
  */
 enum netdev_priv_flags {
 	IFF_802_1Q_VLAN			= 1<<0,
@@ -1290,6 +1291,7 @@ enum netdev_priv_flags {
 	IFF_IPVLAN_MASTER		= 1<<23,
 	IFF_IPVLAN_SLAVE		= 1<<24,
 	IFF_VRF_MASTER			= 1<<25,
+	IFF_NO_QUEUE			= 1<<26,
 };
 
 #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
@@ -1318,6 +1320,7 @@ enum netdev_priv_flags {
 #define IFF_IPVLAN_MASTER		IFF_IPVLAN_MASTER
 #define IFF_IPVLAN_SLAVE		IFF_IPVLAN_SLAVE
 #define IFF_VRF_MASTER			IFF_VRF_MASTER
+#define IFF_NO_QUEUE			IFF_NO_QUEUE
 
 /**
  *	struct net_device - The DEVICE structure.