RDMA/cxgb3: Use ib_device_set_netdev()

This change is required to associate the cxgb3 ib_dev with the
underlying net_device, so in the upcoming patch we can call
ib_device_get_netdev().

Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Link: https://lore.kernel.org/r/20190807103138.17219-3-kamalheib1@gmail.com


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