hwmon: (ftsteutates) Fix clearing alarm sysfs entries

sysfs store functions should return the number of bytes written.
Returning zero results in an endless loop.

Fixes: 08426eda58 ("hwmon: Add driver for FTS BMC chip "Teutates"")
Signed-off-by: Thilo Cestonaro <thilo.cestonaro@ts.fujitsu.com>
[groeck: Clean up documentation change and description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/ftsteutates

@@ -18,6 +18,10 @@ enhancements. It can monitor up to 4 voltages, 16 temperatures and
 8 fans. It also contains an integrated watchdog which is currently
 implemented in this driver.
 
+To clear a temperature or fan alarm, execute the following command with the
+correct path to the alarm file:
+	echo 0 >XXXX_alarm
+
 Specification of the chip can be found here:
 ftp://ftp.ts.fujitsu.com/pub/Mainboard-OEM-Sales/Services/Software&Tools/Linux_SystemMonitoring&Watchdog&GPIO/BMC-Teutates_Specification_V1.21.pdf
 ftp://ftp.ts.fujitsu.com/pub/Mainboard-OEM-Sales/Services/Software&Tools/Linux_SystemMonitoring&Watchdog&GPIO/Fujitsu_mainboards-1-Sensors_HowTo-en-US.pdf