net/mlx5: Lock mlx5 devlink reload callbacks

Change devlink instance locks in mlx5 driver to have devlink reload
callbacks locked, while keeping all driver paths which lead to devl_ API
functions called by the driver locked.

Add mlx5_load_one_devl_locked() and mlx5_unload_one_devl_locked() which
are used by the paths which are already locked such as devlink reload
callbacks.

This patch makes the driver use devl_ API also for traps register as
these functions are called from the driver paths parallel to reload that
requires locking now.

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>