net/mlx4_en: Fix UP limit in ieee_ets->prio_tc

User priority limit has to be less than MLX4_EN_NUM_UP.

Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>