ipv6: Do not warn for informational ICMP messages, regardless of type.

There is no reason to emit a log message for these.

Based upon a suggestion from Hannes Frederic Sowa.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>