ospf6d: OSPFv3 route change comparision fixed for ASBR-only change

ospf6d: OSPFv3 route change comparision fixed for ASBR-only change

When a router route already exists in the area border routers table
as an ABR and it solely changes its ABR or ASBR status, the change
was missed and border route is not updated. This fixes the comparison
for the router_bits in the ospf6_path structure.

This fixes issue https://github.com/FRRouting/frr/issues/16053 although
the actual problem is not the computing router (r2) and not the OSPFv3
redistribution (r3).

Signed-off-by: Acee <aceelindem@gmail.com>
(cherry picked from commit 772688d2d3c03d8eeeb711c2fe3735c9e0885498)