mlx4_core: Fix advertisement of wrong PF context behaviour

Commit 08ff3235 ("mlx4: 64-byte CQE/EQE support") introduced a
regression where older guest VF drivers failed to load even when
64-byte EQEs/CQEs are disabled, since the PF wrongly advertises the
new context behaviour anyway.  The failure looks like:

    mlx4_core 0000:00:07.0: Unknown pf context behaviour
    mlx4_core 0000:00:07.0: Failed to obtain slave caps
    mlx4_core: probe of 0000:00:07.0 failed with error -38

Fix this by basing this advertisement on dev->caps.flags, which is the
operational capabilities used by the QUERY_FUNC_CAP command wrapper
(dev_cap->flags holds the firmware capabilities).
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/net/ethernet/mellanox/mlx4/main.c

@@ -380,7 +380,7 @@ static int mlx4_dev_cap(struct mlx4_dev *dev, struct mlx4_dev_cap *dev_cap)
 		}
 	}
 
-	if ((dev_cap->flags &
+	if ((dev->caps.flags &
 	    (MLX4_DEV_CAP_FLAG_64B_CQE | MLX4_DEV_CAP_FLAG_64B_EQE)) &&
 	    mlx4_is_master(dev))
 		dev->caps.function_caps |= MLX4_FUNC_CAP_64B_EQE_CQE;