net/mlx4: Set vlan stripping policy by the right command

Changing the vlan stripping policy of the QP isn't supported by older
firmware versions for the INIT2RTR command. Nevertheless, we've used it.

Fix that by doing this policy change using INIT2RTR only if the firmware
supports it, otherwise, we call UPDATE_QP command to do the task.

Fixes: 7677fc96

 ('net/mlx4: Strengthen VLAN tags/priorities enforcement in VST mode')
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>