power: supply: sbs-battery: remove unchecked return var

Since the return value is not checked anyhow, we don't need to store it.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/power/supply/sbs-battery.c

@@ -556,7 +556,7 @@ static int sbs_get_battery_serial_number(struct i2c_client *client,
 	if (ret < 0)
 		return ret;
 
-	ret = sprintf(sbs_serial, "%04x", ret);
+	sprintf(sbs_serial, "%04x", ret);
 	val->strval = sbs_serial;
 
 	return 0;