net: dsa: lantiq_gswip: Fix refcount leak in gswip_gphy_fw_list

In the Linux kernel, the following vulnerability has been resolved: net: dsa: lantiq_gswip: Fix refcount leak in gswip_gphy_fw_list Every iteration of for_each_available_child_of_node() decrements the reference count of the previous node. when breaking early from a for_each_available_child_of_node() loop, we need to explicitly call of_node_put() on the gphy_fw_np. Add missing of_node_put() to avoid refcount leak.