bonding: fix 802.3ad support for 14G speed

This patch adds 14 Gbps enum definition, and fixes
aggregated bandwidth calculation based on above slave links.

Fixes: 0d7e2d21 ("IB/ipoib: add get_link_ksettings in ethtool")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>