[IPV6]: Use ipv6_addr_src_scope for link address sorting.

In the source address selection, the address must be sorted
from global to node-local.

But, ifp->scope is different from the scope for source address
selection.

                                 2001::1  fe80::1     ::1
ifp->scope                             0     0x02    0x01
ipv6_addr_src_scope(&ifp->addr)     0x0e     0x02    0x01

So, we need to use ipv6_addr_src_scope(&ifp->addr) for sorting.

And, for backward compatibility, addresses should be sorted from
new one to old one.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Acked-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>