flow_offload: reject offload for all drivers with invalid police parameters

As more police parameters are passed to flow_offload, driver can check
them to make sure hardware handles packets in the way indicated by tc.
The conform-exceed control should be drop/pipe or drop/ok. Besides,
for drop/ok, the police should be the last action. As hardware can't
configure peakrate/avrate/overhead, offload should not be supported if
any of them is configured.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>