net: ena: rss: fix failure to get indirection table

On old hardware, getting / setting the hash function is not supported while
gettting / setting the indirection table is.

This commit enables us to still show the indirection table on older
hardwares by setting the hash function and key to NULL.

Fixes: 1738cd3e ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_ethtool.c

@@ -648,7 +648,21 @@ static int ena_get_rxfh(struct net_device *netdev, u32 *indir, u8 *key,
 	if (rc)
 		return rc;
 
+	/* We call this function in order to check if the device
+	 * supports getting/setting the hash function.
+	 */
 	rc = ena_com_get_hash_function(adapter->ena_dev, &ena_func, key);
+
+	if (rc) {
+		if (rc == -EOPNOTSUPP) {
+			key = NULL;
+			hfunc = NULL;
+			rc = 0;
+		}
+
+		return rc;
+	}
+
 	if (rc)
 		return rc;