tipc: create TIPC_OPEN as a new sk_state

In this commit, we create a new tipc socket state TIPC_OPEN in
sk_state. We primarily replace the SS_UNCONNECTED sock->state with
TIPC_OPEN.

Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>