openvswitch: fix vlan subtraction from packet length

When the packet has its vlan tag in skb->vlan_tci, the length of the VLAN
header is not counted in skb->len. It doesn't make sense to subtract it.

Fixes: 018c1dda

 ("openvswitch: 802.1AD Flow handling, actions, vlan parsing, netlink attributes")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Acked-by: Eric Garver <e@erig.me>
Signed-off-by: David S. Miller <davem@davemloft.net>