net: sparx5: Fix get_stat64 crash in tcpdump

This problem was found with Sparx5 when the tcpdump tool requests the
do_get_stats64 (sparx5_get_stats64) statistic.

The portstats pointer was incorrectly incremented when fetching priority
based statistics.

Fixes: af4b110 (net: sparx5: add ethtool configuration and statistics support)
Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Link: https://lore.kernel.org/r/20220203102900.528987-1-steen.hegelund@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: steen-hegelund-mchp

drivers/net/ethernet/microchip/sparx5/sparx5_ethtool.c

@@ -1103,7 +1103,7 @@ void sparx5_get_stats64(struct net_device *ndev,
 	stats->tx_carrier_errors = portstats[spx5_stats_tx_csense_cnt];
 	stats->tx_window_errors = portstats[spx5_stats_tx_late_coll_cnt];
 	stats->rx_dropped = portstats[spx5_stats_ana_ac_port_stat_lsb_cnt];
-	for (idx = 0; idx < 2 * SPX5_PRIOS; ++idx, ++stats)
+	for (idx = 0; idx < 2 * SPX5_PRIOS; ++idx)
 		stats->rx_dropped += portstats[spx5_stats_green_p0_rx_port_drop
 					       + idx];
 	stats->tx_dropped = portstats[spx5_stats_tx_local_drop];