net: route: Update IPv6 packet routing mechanism

Search destination address in IPv6 neighbor table. If it doesn't
exist in IPv6 neighbor table then go for routing. Added sanitycheck
to verify destination ll address is not the source ll address of
original packet (that means we are re-routing back to original sender).

Change-Id: I24adace6a0d17fbd1d2a36a5d75c79320de0a883
Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>