net: dsa: mv88e6xxx: Use standard helper for broadcast address

Use the conventional declaration style of a MAC address in the
kernel (u8 addr[ETH_ALEN]) for the broadcast address, then set it
using the existing helper.
Signed-off-by: NTobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: NVladimir Oltean <olteanv@gmail.com>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -1968,8 +1968,10 @@ static int mv88e6xxx_set_rxnfc(struct dsa_switch *ds, int port,
 static int mv88e6xxx_port_add_broadcast(struct mv88e6xxx_chip *chip, int port,
 					u16 vid)
 {
-	const char broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 	u8 state = MV88E6XXX_G1_ATU_DATA_STATE_MC_STATIC;
+	u8 broadcast[ETH_ALEN];
+
+	eth_broadcast_addr(broadcast);
 
 	return mv88e6xxx_port_db_load_purge(chip, port, broadcast, vid, state);
 }