hwmon: (w83795) Clear intrusion alarm immediately

When asked to clear the intrusion alarm, do so immediately. We have to
invalidate the cache to make sure the new status will be read. But we
also have to read from the status register once to clear the pending
alarm, as writing to CLR_CHS surprising won't clear it automatically.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>