rtnetlink: remove check for IFLA_IF_NETNSID

RTM_NEWLINK supports the IFLA_IF_NETNSID property since
5bb8ed075428b71492734af66230aa0c07fcc515 so we should not error out
when it is passed.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2802,9 +2802,6 @@ replay:
 	if (err < 0)
 		return err;
 
-	if (tb[IFLA_IF_NETNSID])
-		return -EOPNOTSUPP;
-
 	if (tb[IFLA_IFNAME])
 		nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
 	else