serial: pmac_zilog: use for_each_child_of_node() macro

Use for_each_child_of_node() macro instead of open coding it.

Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Link: https://lore.kernel.org/r/20200916062138.191188-1-miaoqinglang@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>