net/mlx5: Use RMW accessors for changing LNKCTL

[ Upstream commit 30de8725 ]

Don't assume that only the driver would be accessing LNKCTL of the upstream
bridge. ASPM policy changes can trigger write to LNKCTL outside of driver's
control.

Use RMW capability accessors which do proper locking to avoid losing
concurrent updates to the register value.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Fixes: eabe8e5e ("net/mlx5: Handle sync reset now event")
Link: https://lore.kernel.org/r/20230717120503.15276-8-ilpo.jarvinen@linux.intel.com


Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>