net: ethernet: ti: am65-cpsw: setup priority to flow mapping

Now that we support multiple RX queues, enable default priority
to flow mapping so that higher priority packets come on higher
channels (flows).

The Classifier checks for PCP/DSCP priority in the packet and
routes them to the appropriate flow.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>