net: rename local_df to ignore_df

As suggested by several people, rename local_df to ignore_df,
since it means "ignore df bit if it is set".

Cc: Maciej Żenczykowski <maze@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index aa1a9d4..ed0716a 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1073,7 +1073,7 @@
 	}
 
 	/* Queue the packet to IP for output */
-	skb->local_df = 1;
+	skb->ignore_df = 1;
 #if IS_ENABLED(CONFIG_IPV6)
 	if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped)
 		error = inet6_csk_xmit(tunnel->sock, skb, NULL);