net/mlx5e: Refactor tc vlan push/pop actions offloading

Extract actions offloading code to a new function, and also extend data
structures for double vlan actions.

Signed-off-by: Jianbo Liu <jianbol@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>