powerpc/pseries/dlpar: Use helper function for_each_child_of_node()

for_each_child_of_node can help to iterate through the device_node,
and we don't need to use while loop. No functional change with this
conversion.
Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240822085430.25753-3-zhangzekun11@huawei.com

arch/powerpc/platforms/pseries/dlpar.c

@@ -250,11 +250,8 @@ int dlpar_detach_node(struct device_node *dn)
 	struct device_node *child;
 	int rc;
 
-	child = of_get_next_child(dn, NULL);
-	while (child) {
+	for_each_child_of_node(dn, child)
 		dlpar_detach_node(child);
-		child = of_get_next_child(dn, child);
-	}
 
 	rc = of_detach_node(dn);
 	if (rc)