tipc: use destination length for copy string

Got below warning with gcc 8.2 compiler.

net/tipc/topsrv.c: In function ‘tipc_topsrv_start’:
net/tipc/topsrv.c:660:2: warning: ‘strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
  strncpy(srv->name, name, strlen(name) + 1);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/tipc/topsrv.c:660:27: note: length computed here
  strncpy(srv->name, name, strlen(name) + 1);
                           ^~~~~~~~~~~~
So change it to correct length and use strscpy.
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/topsrv.c

@@ -651,7 +651,7 @@ int tipc_topsrv_start(struct net *net)
 	srv->max_rcvbuf_size = sizeof(struct tipc_subscr);
 	INIT_WORK(&srv->awork, tipc_topsrv_accept);
 
-	strncpy(srv->name, name, strlen(name) + 1);
+	strscpy(srv->name, name, sizeof(srv->name));
 	tn->topsrv = srv;
 	atomic_set(&tn->subscription_count, 0);