net: thunderx: add missing of_node_put

for_each_child_of_node performs an of_node_get on each iteration, so
a break out of the loop requires an of_node_put.

A simplified version of the semantic patch that fixes this problem is as
follows (http://coccinelle.lip6.fr):

// <smpl>
@@
local idexpression r.n;
expression r,e;
@@

 for_each_child_of_node(r,n) {
   ...
(
   of_node_put(n);
|
   e = n
|
+  of_node_put(n);
?  break;
)
   ...
 }
... when != n
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cavium/thunder/thunder_bgx.c

@@ -977,8 +977,10 @@ static int bgx_init_of_phy(struct bgx *bgx)
 		SET_NETDEV_DEV(&bgx->lmac[lmac].netdev, &bgx->pdev->dev);
 		bgx->lmac[lmac].lmacid = lmac;
 		lmac++;
-		if (lmac == MAX_LMAC_PER_BGX)
+		if (lmac == MAX_LMAC_PER_BGX) {
+			of_node_put(np_child);
 			break;
+		}
 	}
 	return 0;
 }