ipv6: Pass fib6_result to fib6_table_lookup tracepoint

Change fib6_table_lookup tracepoint to take the fib6_result and use
the fib6_info and fib6_nh from it.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>