mlx5: become aware of when running as a bonding slave

I've been unable to get my hands on suitable supported hardware to date,
but I believe this ought to be all that is needed to enable the mlx5
driver to also work with bonding active-backup crypto offload passthru.

CC: Boris Pismenny <borisp@mellanox.com>
CC: Saeed Mahameed <saeedm@mellanox.com>
CC: Leon Romanovsky <leon@kernel.org>
CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Veaceslav Falico <vfalico@gmail.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: "David S. Miller" <davem@davemloft.net>
CC: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
CC: Jakub Kicinski <kuba@kernel.org>
CC: Steffen Klassert <steffen.klassert@secunet.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: netdev@vger.kernel.org
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>