It seems I missed one change in get_timewait4_sock() to compute
the remaining time before deletion of IPV4 timewait socket.

This could result in wrong output in /proc/net/tcp for tm->when field.

Fixes: 96f817fe ("tcp: shrink tcp6_timewait_sock by one cache line")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>