hwmon: (lm80) Fix missing unlock on error in set_fan_div()

Add the missing unlock before return from function set_fan_div()
in the error handling case.

Fixes: c9c6391551 ("hwmon: (lm80) fix a missing check of the status of SMBus read")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/lm80.c

@@ -393,8 +393,10 @@ static ssize_t set_fan_div(struct device *dev, struct device_attribute *attr,
 	}
 
 	rv = lm80_read_value(client, LM80_REG_FANDIV);
-	if (rv < 0)
+	if (rv < 0) {
+		mutex_unlock(&data->update_lock);
 		return rv;
+	}
 	reg = (rv & ~(3 << (2 * (nr + 1))))
 	    | (data->fan_div[nr] << (2 * (nr + 1)));
 	lm80_write_value(client, LM80_REG_FANDIV, reg);