ethtool: Clean up definitions of rule location arrays in RX NFC

Correct the description of ethtool_rxnfc::rule_locs; it is an array
of currently used locations, not all possible valid locations.

Add note that drivers must not use ethtool_rxnfc::rule_locs.

The rule_locs argument to ethtool_ops::get_rxnfc is either NULL or a
pointer to an array of u32, so change the parameter type accordingly.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/sun/niu.c b/drivers/net/ethernet/sun/niu.c
index cad58f2..5e1e1d2 100644
--- a/drivers/net/ethernet/sun/niu.c
+++ b/drivers/net/ethernet/sun/niu.c
@@ -7303,7 +7303,7 @@
 }
 
 static int niu_get_nfc(struct net_device *dev, struct ethtool_rxnfc *cmd,
-		       void *rule_locs)
+		       u32 *rule_locs)
 {
 	struct niu *np = netdev_priv(dev);
 	int ret = 0;
@@ -7322,7 +7322,7 @@
 		ret = niu_get_ethtool_tcam_entry(np, cmd);
 		break;
 	case ETHTOOL_GRXCLSRLALL:
-		ret = niu_get_ethtool_tcam_all(np, cmd, (u32 *)rule_locs);
+		ret = niu_get_ethtool_tcam_all(np, cmd, rule_locs);
 		break;
 	default:
 		ret = -EINVAL;