openvswitch: use ipgre tunnel rather than gretap tunnel

This allows GRE tunnels to send and receive both
layer 2 packets (packets with an ethernet header) and
layer 3 packets (packets without an ethernet header).

Signed-off-by: Simon Horman <[email protected]>
---
v11
* Make use of skb_mac_header_was_set() to avoid needing to calculate mac_len

v10
* Handle case of l3 only packets on vport-netdev
* Use ARPHRD_NONE for ipgre interfaces as per recent changes in mainline
* Ensure skb->mac_len is set correctly in netdev_port_receive and
  relay on this value to differentiate layer3 packets in
  ovs_flow_key_extract()

v11 release of l3-vpn patch set

v10 release of l3-vpn patch set

v9 release of l3-vpn patch set

Alpha release of l3-vpn for Wed 20 Jan 2016

Alpha release of l3-vpn for Thu 14 Jan 2016

Linux 4.4

Linux 4.4-rc8

Linux 4.4-rc7

Linux 4.4-rc6