This will cause an informative backtrace to print if the user of
ib_device_set_netdev() isn't careful about tearing down the ibdevice
before its the netdevice parent is destroyed. Such as like this:

  unregister_netdevice: waiting for vlan0 to become free. Usage count = 2
  leaked reference.
   ib_device_set_netdev+0x266/0x730
   siw_newlink+0x4e0/0xfd0
   nldev_newlink+0x35c/0x5c0
   rdma_nl_rcv_msg+0x36d/0x690
   rdma_nl_rcv+0x2ee/0x430
   netlink_unicast+0x543/0x7f0
   netlink_sendmsg+0x918/0xe20
   sock_sendmsg+0xcf/0x120
   ____sys_sendmsg+0x70d/0x8b0
   ___sys_sendmsg+0x11d/0x1b0
   __sys_sendmsg+0xfa/0x1d0
   do_syscall_64+0x35/0xb0
   entry_SYSCALL_64_after_hwframe+0x63/0xcd

This will help debug the issues syzkaller is seeing.
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v1-a7c81b3842ce+e5-netdev_tracker_jgg@nvidia.comSigned-off-by: NLeon Romanovsky <leon@kernel.org>