tsnep: Remove useless null check before call of_node_put()

No need to add null check before call of_node_put(), since the
implementation of of_node_put() has done it.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Link: https://lore.kernel.org/r/1650509283-26168-1-git-send-email-baihaowen@meizu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Lotte-Bai

drivers/net/ethernet/engleder/tsnep_main.c

@@ -1091,8 +1091,7 @@ static int tsnep_mdio_init(struct tsnep_adapter *adapter)
 	retval = of_mdiobus_register(adapter->mdiobus, np);
 
 out:
-	if (np)
-		of_node_put(np);
+	of_node_put(np);
 
 	return retval;
 }