drivers: thermal: processor_thermal_device: Fix build warning

As a system sleep callback, proc_thermal_resume() should be defined only
if CONFIG_PM_SLEEP is defined.

This fixes a build warning when CONFIG_PM_SLEEP is not set,
drivers/thermal/intel/int340x_thermal/processor_thermal_device.c:446:12: error: 'proc_thermal_resume' defined but not used [-Werror=unused-function]
 static int proc_thermal_resume(struct device *dev)

Fixes: aaba9791 ("drivers: thermal: processor_thermal: Read PPCC on resume")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>