net: ethernet: ti: am65-cpsw: Fix mdio cleanup in probe

In the am65_cpsw_nuss_probe() function's cleanup path, the call to
of_platform_device_destroy() for the common->mdio_dev device is invoked
unconditionally. It is possible that either the MDIO node is not present
in the device-tree, or the MDIO node is disabled in the device-tree. In
both these cases, the MDIO device is not created, resulting in a NULL
pointer dereference when the of_platform_device_destroy() function is
invoked on the common->mdio_dev device on the cleanup path.

Fix this by ensuring that the common->mdio_dev device exists, before
attempting to invoke of_platform_device_destroy().

Fixes: a45cfcc6 ("net: ethernet: ti: am65-cpsw-nuss: use of_platform_device_create() for mdio")
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20230403090321.835877-1-s-vadapalli@ti.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/ti/am65-cpsw-nuss.c

@@ -2926,7 +2926,8 @@ static int am65_cpsw_nuss_probe(struct platform_device *pdev)
 	am65_cpsw_nuss_phylink_cleanup(common);
 	am65_cpts_release(common->cpts);
 err_of_clear:
-	of_platform_device_destroy(common->mdio_dev, NULL);
+	if (common->mdio_dev)
+		of_platform_device_destroy(common->mdio_dev, NULL);
 err_pm_clear:
 	pm_runtime_put_sync(dev);
 	pm_runtime_disable(dev);
@@ -2956,7 +2957,8 @@ static int am65_cpsw_nuss_remove(struct platform_device *pdev)
 	am65_cpts_release(common->cpts);
 	am65_cpsw_disable_serdes_phy(common);
 
-	of_platform_device_destroy(common->mdio_dev, NULL);
+	if (common->mdio_dev)
+		of_platform_device_destroy(common->mdio_dev, NULL);
 
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);