net/mlx5e: Block offload of outer header csum for UDP tunnels

[ Upstream commit 6d6727dd ]

The device is able to offload either the outer header csum or inner
header csum. The driver utilizes the inner csum offload. Hence, block
setting of tx-udp_tnl-csum-segmentation and set it to off[fixed].

Fixes: b49663c8

 ("net/mlx5e: Add support for UDP tunnel segmentation with outer checksum offload")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>