net: route: Try to route IPv6 packet if we are not the recipient

Instead of simply dropping the packet if the destination IPv6
address is not ours, try to figure out if there is a route
to real destination and then re-route the IPv6 packet there.

Change-Id: I6b2a0d7096b3d7877b82b04f38e3a6e588587c11
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>