net/mlx5: Lag, add net namespace support

net/mlx5: Lag, add net namespace support

Update the LAG implementation to support net namespace isolation.
Recent devcom changes added namespace-aware client matching. Align LAG
with this model so that hardware LAG forms only between mlx5 interfaces
that share the same network namespace. This avoids cross-namespace
interference and matches user expectations when devices are placed in
different netns.

Make LAG netns-aware by storing the device’s namespace in mlx5_lag and
registering the devcom client with that namespace. As a result, only
peers in the same netns are eligible to form a LAG.
Adjust reload handling so LAG teardown/re-evaluation happens in the
correct namespace context. Remove the blanket restriction that prevented
devlink reload when LAG was active. Remove the reload restriction here
allowing devlink reload in LAG mode is part of delivering complete netns
aware LAG support:

With per-netns devcom registration, reload no longer risks
cross-namespace coupling. The devcom client is torn down and
re-registered in the device’s current netns, and LAG is re-evaluated
within that scope. The change is trivial and self-contained, and keeping
it in this patch avoids splitting a feature that is functionally one
unit.

Only devices in same netns can form hardware LAG.
devlink reload no longer fails just because LAG is active.
LAG is torn down/re-created as needed within the correct namespace.
No change for setups that don’t use namespaces.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1757940070-618661-5-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>