net: qos: police action add index for tc flower offloading

Hardware device may include more than one police entry. Specifying the
action's index make it possible for several tc filters to share the same
police action when installing the filters.

Propagate this index to device drivers through the flow offload
intermediate representation, so that drivers could share a single
hardware policer between multiple filters.

v1->v2 changes:
- Update the commit message suggest by Ido Schimmel <idosch@idosch.org>

Signed-off-by: Po Liu <Po.Liu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>