net: microchip: sparx5: Add support for TC flower filter statistics

This provides flower filter packet statistics (bytes are not supported) via
the dedicated IS2 counter feature.

All rules having the same TC cookie will contribute to the packet
statistics for the filter as they are considered to be part of the same TC
flower filter.

Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>