net: dsa: bcm_sf2: Add support for ethtool::rxnfc

Add support for configuring classification rules using the
ethtool::rxnfc API.  This is useful to program the switch's CFP/TCAM to
redirect specific packets to specific ports/queues for instance. For
now, we allow any kind of IPv4 5-tuple matching.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>