net: hns: Add missing fwnode_handle_put in hns_mac_init

In one of the error paths of the device_for_each_child_node() loop
in hns_mac_init, add missing call to fwnode_handle_put.

Signed-off-by: Peng Wu <wupeng58@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>