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.