net: vlan: Add parse protocol header ops

Add parse protocol header ops for vlan device. Before this patch, vlan
tagged packet transmitted by af_packet had skb->protocol unset. Some
kernel methods (like __skb_flow_dissect()) rely on this missing information
for its packet processing.

Signed-off-by: Eran Ben Elisha <eranbe@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>