Fix dpdk/ldradix fib lookup algorithm preference calculation.

The current preference number were copied from IPv4 code,
assuming 500k routes to be the full-view. Adjust with the current
reality (100k full-view).

Reported by: Marek Zarychta <zarychtam at plan-b.pwste.edu.pl>

(cherry picked from commit d5be41beb7c44119730791d92782d8e77174d312)