net/mlx5: Drain health before unregistering devlink

[ Upstream commit 824c8dc4 ]

mlx5 health mechanism is using devlink APIs, which are using devlink
notify APIs. After the cited patch, using devlink notify APIs after
devlink is unregistered triggers a WARN_ON().
Hence, drain health WQ before devlink is unregistered.

Fixes: cf530217 ("devlink: Notify users when objects are accessible")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>