nfp: flower: add support for packet-per-second policing

Allow hardware offload of a policer action attached to a matchall filter
which enforces a packets-per-second rate-limit.

e.g.
tc filter add dev tap1 parent ffff: u32 match \
        u32 0 0 police pkts_rate 3000 pkts_burst 1000

Signed-off-by: Peng Zhang <peng.zhang@corigine.com>
Signed-off-by: Baowen Zheng <baowen.zheng@corigine.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Louis Peens <louis.peens@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>