CVE-2025-68187

In the Linux kernel, the following vulnerability has been resolved:

net: mdio: Check regmap pointer returned by device_node_to_regmap()

The call to device_node_to_regmap() in airoha_mdio_probe() can return
an ERR_PTR() if regmap initialization fails. Currently, the driver
stores the pointer without validation, which could lead to a crash
if it is later dereferenced.

Add an IS_ERR() check and return the corresponding error code to make
the probe path more robust.