hwmon: (adm1029) Ensure the fan_div cache is updated in set_fan_div

commit 1035a9e3 upstream.

Writing to fanX_div does not clear the cache. As a result, reading
from fanX_div may return the old value for up to two seconds
after writing a new value.

This patch ensures the fan_div cache is updated in set_fan_div().
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/hwmon/adm1029.c

@@ -228,6 +228,9 @@ static ssize_t set_fan_div(struct device *dev,
 	/* Update the value */
 	reg = (reg & 0x3F) | (val << 6);
 
+	/* Update the cache */
+	data->fan_div[attr->index] = reg;
+
 	/* Write value */
 	i2c_smbus_write_byte_data(client,
 				  ADM1029_REG_FAN_DIV[attr->index], reg);