When IB device is undergoing unregistration, the GID cache is always
cleaned up after all clients are unregistered with the below flow.

__ib_unregister_device()
  disable_device()
  ib_cache_cleanup_one()
    gid_table_cleanup_one()
      cleanup_gid_table_port()

There is no use in generating a GID change event at this stage, where
there is no active client of the device and device is nearly unregistered.

Link: https://lore.kernel.org/r/20191020065427.8772-4-leon@kernel.orgSigned-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>