net: ibm: fix possible object reference leak

The call to ehea_get_eth_dn returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
./drivers/net/ethernet/ibm/ehea/ehea_main.c:3163:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 3154, but without a corresponding object release within this function.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Douglas Miller <dougmill@linux.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ehea/ehea_main.c

@@ -3160,6 +3160,7 @@ static ssize_t ehea_probe_port(struct device *dev,
 
 	if (ehea_add_adapter_mr(adapter)) {
 		pr_err("creating MR failed\n");
+		of_node_put(eth_dn);
 		return -EIO;
 	}