net: Convert fib_* pernet_operations, registered via subsys_initcall

Both of them create and initialize lists, which are not touched
by another foreing pernet_operations.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>