hwmon: (it87) Invalidate cache on temperature sensor change

When any temperature sensor type is changed, the corresponding
temperature value needs to be updated. The register caching mechanism
may delay this update, so we want to invalidate the cache to force an
immediate update.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --cc drivers/hwmon/it87.c
Simple merge