team: refine IFF_XMIT_DST_RELEASE capability

Cloned patch of Eric Dumazet for bonding.

Some workloads greatly benefit of IFF_XMIT_DST_RELEASE capability
on output net device, avoiding dirtying dst refcount.

team currently disables IFF_XMIT_DST_RELEASE unconditionally.

If all ports have the IFF_XMIT_DST_RELEASE bit set, then
team dev can also have it in its priv_flags.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>