hwmon: (pmbus) Clear sensor data after chip write

Set the sensor->data field to -ENODATA to force a chip access next time
the sensor value is read.

Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
Link: https://lore.kernel.org/r/20210201195929.1200-2-erik.rosen@metormote.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>