[IPV6]: Replace bogus instances of inet->recverr

While looking at this problem I noticed that IPv6 was sometimes
looking at inet->recverr which is bogus.  Here is a patch to
correct that and use np->recverr.
 
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>