EDAC/versalnet: Fix device_node leak in mc_probe()

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

EDAC/versalnet: Fix device_node leak in mc_probe()

of_parse_phandle() returns a device_node reference that must be released with

of_node_put(). The original code never freed r5_core_node on any exit path,

causing a memory leak.

Fix this by using the automatic cleanup attribute __free(device_node) which

ensures of_node_put() is called when the variable goes out of scope.