mlxsw: spectrum: Add support for vlan modify TC action

Add VLAN action offloading. Invoke it from Spectrum flower handler for
"vlan modify" actions.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>