net/mlx5e: Use correct eswitch for stack devices with lag

If link aggregation is used within stack devices driver rejects encap
rules if PF of the VF tunnel device is down. This happens because route
resolved for other PF and its eswitch instance is used to determine
correct vport.
To fix that use devcom feature to retrieve other eswitch instance if
failed to find vport for the 1st eswitch and LAG is active.

Fixes: 10742efc ("net/mlx5e: VF tunnel TX traffic offloading")
Signed-off-by: Dmytro Linkin <dlinkin@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>