IB/mlx4: Set traffic class in AH

Set traffic class within sl_tclass_flowlabel when create iboe AH.
Without this the TOS value will be empty when running VLAN tagged
traffic, because the TOS value is taken from the traffic class in the
address handle attributes.

Fixes: 9106c410 ('IB/mlx4: Fix SL to 802.1Q priority-bits mapping for IBoE')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>