ravb: Add tx_counters to struct ravb_hw_info

The register for retrieving TX counters is present only on R-Car Gen3
and RZ/G2L; it is not present on R-Car Gen2.

Add the tx_counters hw feature bit to struct ravb_hw_info, to enable this
feature specifically for R-Car Gen3 now and later extend it to RZ/G2L.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/ravb.h

@@ -1000,6 +1000,7 @@ struct ravb_hw_info {
 
 	/* hardware features */
 	unsigned internal_delay:1;	/* AVB-DMAC has internal delays */
+	unsigned tx_counters:1;		/* E-MAC has TX counters */
 };
 
 struct ravb_private {

drivers/net/ethernet/renesas/ravb_main.c

@@ -1632,13 +1632,14 @@ static u16 ravb_select_queue(struct net_device *ndev, struct sk_buff *skb,
 static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
 {
 	struct ravb_private *priv = netdev_priv(ndev);
+	const struct ravb_hw_info *info = priv->info;
 	struct net_device_stats *nstats, *stats0, *stats1;
 
 	nstats = &ndev->stats;
 	stats0 = &priv->stats[RAVB_BE];
 	stats1 = &priv->stats[RAVB_NC];
 
-	if (priv->chip_id == RCAR_GEN3) {
+	if (info->tx_counters) {
 		nstats->tx_dropped += ravb_read(ndev, TROCR);
 		ravb_write(ndev, 0, TROCR);	/* (write clear) */
 	}
@@ -1937,6 +1938,7 @@ static const struct ravb_hw_info ravb_gen3_hw_info = {
 	.stats_len = ARRAY_SIZE(ravb_gstrings_stats),
 	.max_rx_len = RX_BUF_SZ + RAVB_ALIGN - 1,
 	.internal_delay = 1,
+	.tx_counters = 1,
 };
 
 static const struct ravb_hw_info ravb_gen2_hw_info = {