openvswitch: pass mac_proto to ovs_vport_send

We'll need it to alter packets sent to ARPHRD_NONE interfaces.

Change do_output() to use the actual L2 header size of the packet when
deciding on the minimum cutlen. The assumption here is that what matters is
not the output interface hard_header_len but rather the L2 header of the
particular packet. For example, ARPHRD_NONE tunnels that encapsulate
Ethernet should get at least the Ethernet header.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>