bridge: avoid br_ifinfo_notify when nothing changed

When neither IFF_BRIDGE nor IFF_BRIDGE_PORT is set,
and afspec == NULL but  protinfo != NULL, we run into
"if (err == 0) br_ifinfo_notify(RTM_NEWLINK, p);" with
random value in ret.

Thanks to Sergei for pointing out the error in commit comments.
Signed-off-by: NHong Zhiguo <honkiko@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/br_netlink.c

@@ -357,7 +357,7 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh)
 	struct nlattr *afspec;
 	struct net_bridge_port *p;
 	struct nlattr *tb[IFLA_BRPORT_MAX + 1];
-	int err;
+	int err = 0;
 
 	ifm = nlmsg_data(nlh);
 
@@ -370,7 +370,7 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh)
 	/* We want to accept dev as bridge itself if the AF_SPEC
 	 * is set to see if someone is setting vlan info on the brigde
 	 */
-	if (!p && ((dev->priv_flags & IFF_EBRIDGE) && !afspec))
+	if (!p && !afspec)
 		return -EINVAL;
 
 	if (p && protinfo) {