tcp: also NULL skb->dev when copy was needed

In rare cases retransmit logic will make a full skb copy, which will not
trigger the zeroing added in recent change
b738a185 ("tcp: ensure skb->dev is NULL before leaving TCP stack").

Cc: Eric Dumazet <edumazet@google.com>
Fixes: 75c119af ("tcp: implement rb-tree based retransmit queue")
Fixes: 28f8bfd1 ("netfilter: Support iif matches in POSTROUTING")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>