rtnetlink: Don't ignore IFLA_TARGET_NETNSID when ifname is specified in rtnl_dellink().

The cited commit accidentally replaced tgt_net with net in rtnl_dellink().

As a result, IFLA_TARGET_NETNSID is ignored if the interface is specified
with IFLA_IFNAME or IFLA_ALT_IFNAME.

Let's pass tgt_net to rtnl_dev_get().

Fixes: cc6090e9 ("net: rtnetlink: introduce helper to get net_device instance by ifname")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -3288,7 +3288,7 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (ifm->ifi_index > 0)
 		dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
 	else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME])
-		dev = rtnl_dev_get(net, tb);
+		dev = rtnl_dev_get(tgt_net, tb);
 	else if (tb[IFLA_GROUP])
 		err = rtnl_group_dellink(tgt_net, nla_get_u32(tb[IFLA_GROUP]));
 	else