net: mdio: Add mdio_free() and mdio_unregister() API

Currently there is no API to uninitialize mdio. Add two APIs for this.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/common/miiphyutil.c b/common/miiphyutil.c
index c88c28a..e499b58 100644
--- a/common/miiphyutil.c
+++ b/common/miiphyutil.c
@@ -152,6 +152,11 @@
 	return bus;
 }
 
+void mdio_free(struct mii_dev *bus)
+{
+	free(bus);
+}
+
 int mdio_register(struct mii_dev *bus)
 {
 	if (!bus || !bus->name || !bus->read || !bus->write)
@@ -173,6 +178,20 @@
 	return 0;
 }
 
+int mdio_unregister(struct mii_dev *bus)
+{
+	if (!bus)
+		return 0;
+
+	/* delete it from the list */
+	list_del(&bus->link);
+
+	if (current_mii == bus)
+		current_mii = NULL;
+
+	return 0;
+}
+
 void mdio_list_devices(void)
 {
 	struct list_head *entry;