devlink: remove linecards lock

Similar to other devlink objects, convert the linecards list to be
protected by devlink instance lock. Alongside with that rename the
create/destroy() functions to devl_* to indicate the devlink instance
lock needs to be held while calling them.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>