tipc: fix a double free in tipc_enable_bearer()

bearer_disable() already calls kfree_rcu() to free struct tipc_bearer,
we don't need to call kfree() again.

Fixes: cb30a63384bc ("tipc: refactor function tipc_enable_bearer()")
Reported-by: [e-mail]
Cc: Ying Xue <[e-mail]>
Cc: Jon Maloy <[e-mail]>
Signed-off-by: Cong Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/tipc/bearer.c

···
 	res = tipc_disc_create(net, b, &b->bcast_addr, &skb);
 	if (res) {
 		bearer_disable(net, b);
-		kfree(b);
 		errstr = "failed to create discoverer";
 		goto rejected;
 	}