hwmon: (coretemp) don't use kernel assigned CPU number as platform device ID

... as that has the potential to conflict with (particularly soft) CPU
hot removal and re-adding.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
[guenter.roeck@ericsson.com: use platform device ID as physical CPU id]
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>