vlan: kill vlan_put_tag helper

Since both tx and rx paths work with skb->vlan_tci, there's no need for
this function anymore. Switch users directly to __vlan_hwaccel_put_tag.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>