net: ethtool: pse-pd: Fix possible null-deref

In the Linux kernel, the following vulnerability has been resolved: net: ethtool: pse-pd: Fix possible null-deref Fix a possible null dereference when a PSE supports both c33 and PoDL, but only one of the netlink attributes is specified. The c33 or PoDL PSE capabilities are already validated in the ethnl_set_pse_validate() call.