hwmon: ({core, pkg, via-cpu}temp) remove unnecessary CONFIG_HOTPLUG_CPU ifdefs

CONFIG_HOTPLUG_CPU is used too much in some drivers.
This patch clean them up.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>