net: phy: xilinx: Break while loop over ethernet phy

The commit 6c993815bbea ("net: phy: xilinx: Be compatible with live OF
tree") change driver behavior to while loop which wasn't correct because
the driver was looping over again and again. The reason was that
ofnode_valid() is taking 0 as correct value.
Fix it by changing while loop to ofnode_for_each_subnode() which is only
loop over available nodes.

Fixes: 6c993815bbea ("net: phy: xilinx: Be compatible with live OF tree")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index dcdef9e..ed197fa 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -948,9 +948,9 @@
 						 phy_interface_t interface)
 {
 	struct phy_device *phydev = NULL;
-	ofnode node = dev_ofnode(dev);
+	ofnode node;
 
-	while (ofnode_valid(node)) {
+	ofnode_for_each_subnode(node, dev_ofnode(dev)) {
 		node = ofnode_by_compatible(node, "xlnx,gmii-to-rgmii-1.0");
 		if (ofnode_valid(node)) {
 			phydev = phy_device_create(bus, 0,