The node discovery domain is assigned when a bearer is enabled.
In the previous commit we reflect this attribute directly in the
bearer structure since it's needed to reinitialize the node
discovery mechanism after a hardware address change.

There's no need to replicate this attribute anywhere else, so we
remove it from the tipc_link_req structure.
Signed-off-by: NErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: NYing Xue <ying.xue@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>