[IPV6]: Fix NS handing for proxy/anycast address

Timer set up by pneigh_enqueue() ended up calling ndisc_rcv()
via pndisc_redo(), which clears LOCALLY_ENQUEUED flag in
NEIGH_CB(skb) and NS was queued again.
Let's call ndisc_recv_ns() directly to avoid the loop.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>