net: dsa: ksz: ksz8863_smi_probe: fix possible NULL pointer dereference

Fix possible NULL pointer dereference in case devm_kzalloc() failed to
allocate memory.

Fixes: 60a3647 ("net: dsa: microchip: Add Microchip KSZ8863 SMI based driver support")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz8863_smi.c

@@ -147,6 +147,9 @@ static int ksz8863_smi_probe(struct mdio_device *mdiodev)
 	int i;
 
 	ksz8 = devm_kzalloc(&mdiodev->dev, sizeof(struct ksz8), GFP_KERNEL);
+	if (!ksz8)
+		return -ENOMEM;
+
 	ksz8->priv = mdiodev;
 
 	dev = ksz_switch_alloc(&mdiodev->dev, ksz8);