rtnetlink: check DO_SETLINK_NOTIFY correctly in do_setlink

The check 'status & DO_SETLINK_NOTIFY' in do_setlink doesn't really
work after status & DO_SETLINK_MODIFIED, as:

  DO_SETLINK_MODIFIED 0x1
  DO_SETLINK_NOTIFY 0x3

Considering that notifications are suppposed to be sent only when
status have the flag DO_SETLINK_NOTIFY, the right check would be:

  (status & DO_SETLINK_NOTIFY) == DO_SETLINK_NOTIFY

This would avoid lots of duplicated notifications when setting some
properties of a link.

Fixes: ba998906 ("rtnl/do_setlink(): notify when a netdev is modified")
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NDavid Ahern <dsahern@gmail.com>
Acked-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2248,7 +2248,7 @@ static int do_setlink(const struct sk_buff *skb,
 
 errout:
 	if (status & DO_SETLINK_MODIFIED) {
-		if (status & DO_SETLINK_NOTIFY)
+		if ((status & DO_SETLINK_NOTIFY) == DO_SETLINK_NOTIFY)
 			netdev_state_change(dev);
 
 		if (err < 0)