mlxsw: spectrum_acl: Offload FLOW_ACTION_POLICE

Offload action police when used with a flower classifier. The number of
dropped packets is read from the policer and reported to tc.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>