net: dsa: microchip: add error checking for ksz_pwrite

Add status validation for port register write inside
lan937x_change_mtu. ksz_pwrite and ksz_pread api's are
updated with return type int (Reference patch mentioned
below). Update lan937x_change_mtu with status validation
for ksz_pwrite16().

Link: https://patchwork.kernel.org/project/netdevbpf/patch/20220826105634.3855578-6-o.rempel@pengutronix.de/Signed-off-by: Rakesh Sankaranarayanan <rakesh.sankaranarayanan@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/lan937x_main.c

@@ -242,7 +242,11 @@ int lan937x_change_mtu(struct ksz_device *dev, int port, int new_mtu)
 	}
 
 	/* Write the frame size in PORT_MAX_FR_SIZE register */
-	ksz_pwrite16(dev, port, PORT_MAX_FR_SIZE, new_mtu);
+	ret = ksz_pwrite16(dev, port, PORT_MAX_FR_SIZE, new_mtu);
+	if (ret) {
+		dev_err(ds->dev, "failed to update mtu for port %d\n", port);
+		return ret;
+	}
 
 	return 0;
 }