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: cb30a633 ("tipc: refactor function tipc_enable_bearer()")
Reported-by: syzbot+b981acf1fb240c0c128b@syzkaller.appspotmail.com
Cc: Ying Xue <ying.xue@windriver.com>
Cc: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tipc/bearer.c

@@ -319,7 +319,6 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 	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;
 	}