iavf: use unregister_netdev

iavf: use unregister_netdev

Use unregister_netdev, which takes rtnl_lock for us. We don't have to
check the reg_state under rtnl_lock. There's nothing to race with. We
have just cancelled the finish_config work.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20231027175941.1340255-7-jacob.e.keller@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>