thermal: core: move emul_temp creation to tz->device.groups

emul_temp creation is dependent on a compile time
condition. Moving to tz->device.groups.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>