[NETNS][IPV6] fix some missing namespace

This patch adds some missing namespace

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/ipv6/ip6_output.c
Simple merge

diff --cc net/ipv6/ipv6_sockglue.c
Simple merge

diff --cc net/ipv6/route.c
Simple merge