net/ipv6: Update fib6 tracepoint to take fib6_info

Similar to IPv4, IPv6 should use the FIB lookup result in the
tracepoint.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>