net: pktgen: disable xmit_clone on virtual devices

net: pktgen: disable xmit_clone on virtual devices

Trying to use burst capability (aka xmit_more) on a virtual device
like bonding is not supported.

For example, skb might be queued multiple times on a qdisc, with
various list corruptions.

Fixes: 38b2cf2982dc ("net: pktgen: packet bursting via skb->xmit_more")
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>