team: add ethtool get_link_ksettings

Like bond, add ethtool get_link_ksettings to show the total speed.

v2: no update, just repost.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>