hwmon: (ltc4261) set data->valid to 0 if error

If there is an error it is better to set data->valid to 0
so the next call to ltc4261_update_device will always be
executed.
Signed-off-by: Frans Meulenbroeks <fransmeulenbroeks@gmail.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

drivers/hwmon/ltc4261.c

@@ -85,6 +85,7 @@ static struct ltc4261_data *ltc4261_update_device(struct device *dev)
 					"Failed to read ADC value: error %d\n",
 					val);
 				ret = ERR_PTR(val);
+				data->valid = 0;
 				goto abort;
 			}
 			data->regs[i] = val;