IB/mlx4: Put priority bits in WQE of IBoE MLX QP

Otherwise CM packets going over MLX QP1 get fixed scheduling priority 0.
We want CM packets to get the same scheduling priority, and therefore
map to the same SQ (Schedule Queue) and eventually TC (Traffic Class),
as the application requested for the actual QP used for the connection.

Signed-off-by: Oren Duer <oren@mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>