net: dsa: b53: Only call b53_port_event() for SGMII ports

Built-in PHY ports are still being polled, avoid generating spurious
and duplicate events which the PHY library resolves through polling
anyways.

Fixes: 0e01491d ("net: dsa: b53: Add SerDes support")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_srab.c

@@ -373,7 +373,8 @@ static irqreturn_t b53_srab_port_thread(int irq, void *dev_id)
 	struct b53_srab_port_priv *port = dev_id;
 	struct b53_device *dev = port->dev;
 
-	b53_port_event(dev->ds, port->num);
+	if (port->mode == PHY_INTERFACE_MODE_SGMII)
+		b53_port_event(dev->ds, port->num);
 
 	return IRQ_HANDLED;
 }