If output device wants to see the dst, inherit the dst of the original skb
in the ndisc request.

This is an IPv6 counterpart of commit 0accfc26 ("arp: Inherit metadata
dst when creating ARP requests").
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>