net: lan9303: Fix read error execution path

[ Upstream commit 8964916 ]

This patch fixes an issue where a read failure of a port statistic counter
will return unknown results.  While it is highly unlikely the read will
ever fail, it is much cleaner to return a zero for the stat count.

Fixes: a129259 ("net: dsa: add new DSA switch driver for the SMSC-LAN9303")
Signed-off-by: Jerry Ray <jerry.ray@microchip.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20221209153502.7429-1-jerry.ray@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/dsa/lan9303-core.c

@@ -1003,9 +1003,11 @@ static void lan9303_get_ethtool_stats(struct dsa_switch *ds, int port,
 		ret = lan9303_read_switch_port(
 			chip, port, lan9303_mib[u].offset, &reg);
 
-		if (ret)
+		if (ret) {
 			dev_warn(chip->dev, "Reading status port %d reg %u failed\n",
 				 port, lan9303_mib[u].offset);
+			reg = 0;
+		}
 		data[u] = reg;
 	}
 }