thermal: hide CONFIG_THERMAL_HWMON

It's about time to revert 16d75239 ("thermal: Create
CONFIG_THERMAL_HWMON=n").  Anybody running a kernel >= 2.6.40 would also
be running a recent enough version of lm-sensors.

Actually having CONFIG_THERMAL_HWMON is pretty convenient so instead of
dropping it, we keep it but hide it.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Rene Herman <rene.herman@gmail.com>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>