RDMA/mlx5: Annotate lock dependency in bind/unbind slave port

NULL-ing notifier_call is performed under protection
of mlx5_ib_multiport_mutex lock. Such protection is
not easily spotted and better to be guarded by lockdep
annotation.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/20190813102814.22350-1-leon@kernel.org


Signed-off-by: Doug Ledford <dledford@redhat.com>