net: ethernet: rtsn: Fix a null pointer dereference in rtsn_probe()

Add check for the return value of rcar_gen4_ptp_alloc()
to prevent potential null pointer dereference.

Fixes: b0d3969 ("net: ethernet: rtsn: Add support for Renesas Ethernet-TSN")
Cc: stable@vger.kernel.org
Signed-off-by: Haoxiang Li <haoxiang_li2024@163.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://patch.msgid.link/20250703100109.2541018-1-haoxiang_li2024@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Haoxiang Li

drivers/net/ethernet/renesas/rtsn.c

@@ -1259,7 +1259,12 @@ static int rtsn_probe(struct platform_device *pdev)
 	priv = netdev_priv(ndev);
 	priv->pdev = pdev;
 	priv->ndev = ndev;
+
 	priv->ptp_priv = rcar_gen4_ptp_alloc(pdev);
+	if (!priv->ptp_priv) {
+		ret = -ENOMEM;
+		goto error_free;
+	}
 
 	spin_lock_init(&priv->lock);
 	platform_set_drvdata(pdev, priv);