bonding: handle more gso types

In commit 5a7baa78 ("bonding: Advertize vxlan offload features when
supported"), Or Gerlitz added support conditional vxlan offload.

In this patch I also add support for all kind of tunnels,
but we allow a bonding device to not require segmentation,
as it is always better to make this segmentation at the very last stage,
if a particular slave device requires it.

Tested:

 Setup a GRE tunnel,
 on a physical NIC not having tx-gre-segmentation.
 Results on bnx2x are even better, as we no longer have to segment
 in software.

ethtool -K bond0 tx-gre-segmentation off

super_netperf 50 --google-pacing-rate 30000000 -H 10.7.8.152 -l 15
7538.32

ethtool -K bond0 tx-gre-segmentation on

super_netperf 50 --google-pacing-rate 30000000 -H 10.7.8.152 -l 15
10200.5

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>