net: amd: add missing of_node_put()

of_find_node_by_path() acquires a reference to the node
returned by it and that reference needs to be dropped by its caller.
This place doesn't do that, so fix it.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>