net: netcp: add missing of_node_put() in netcp_probe()

This node pointer is returned by of_get_child_by_name() with refcount
incremented in this function. of_node_put() on it before exitting this
function.

This is detected by Coccinelle semantic patch.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>