net/mlx5: LAG, Fix off-by-one in single-FDB error rollback

net/mlx5: LAG, Fix off-by-one in single-FDB error rollback

On failure at index i, the reverse cleanup loop in
mlx5_lag_create_single_fdb() starts from i, so the failed index
itself is rolled back. That can operate on uninitialized state or
double-tear-down a rule the add_one path already self-rolled-back.

Start the rollback from i - 1 so only successfully-installed entries
are undone.

Fixes: ddbb5ddc43ad ("net/mlx5: LAG, Refactor lag logic")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260630112917.698313-2-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>