[VLAN]: Fix nested VLAN transmit bug

[ Upstream commit: 6ab3b487 ]

Fix misbehavior of vlan_dev_hard_start_xmit() for recursive encapsulations.
Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>