net: dsa: lan9303: Transmit using ALR when unicast

lan9303_xmit_use_arl() introduced in previous patch set is wrong.
The chip flood broadcast and unknown multicast frames. The effect is that
broadcasts and multicasts are duplicated on egress. It is not possible to
configure the chip to direct unknown multicasts to CPU port only.

This means that only unicast frames can be transmitted using ALR lookup.

Signed-off-by: Egil Hjelmeland <privat@egil-hjelmeland.no>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>