net/mlx4_core: Fix namespace misalignment in QinQ VST support commit

The cited commit introduced the following new enum value in file
include/linux/mlx4/device.h:

    MLX4_DEV_CAP_FLAG2_SVLAN_BY_QP

However the value of MLX4_DEV_CAP_FLAG2_SVLAN_BY_QP needs to stay
consistent with the value used in another namespace in
function dump_dev_cap_flags2(), which is manually kept in sync.
The change here restores that consistency.

Fixes: 7c3d21c8 ("net/mlx4_core: Preparation for VF vlan protocol 802.1ad")
Reported-by: Mukesh Kacker <mukesh.kacker@oracle.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>