ixgbe: support L2 tunnel operations

ixgbe: support L2 tunnel operations

Add support of l2 tunnel configuration and operations.
1, Support modifying ether type of a type of l2 tunnel.
2, Support enabling and disabling the support of a type of l2 tunnel.
3, Support enabling/disabling l2 tunnel tag insertion/stripping.
4, Support enabling/disabling l2 tunnel packets forwarding.
5, Support adding/deleting forwarding rules for l2 tunnel packets.
Only support E-tag now.

Also update the release note.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
Acked-by: Shaopeng He <shaopeng.he@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>
Tested-by: Yong Liu <yong.liu@intel.com>