ACPI / thermal: fix thermal driver compile error when CONFIG_PM_SLEEP is undefined

The ACPI thermal driver defines acpi_thermal_resume() when
CONFIG_PM_SLEEP is defined. This results in the following compile
error when CONFIG_PM_SLEEP is undefined.

  CC      drivers/acpi/thermal.o
drivers/acpi/thermal.c:107:8: error: ‘acpi_thermal_resume’ undeclared here (not in a function)
make[2]: *** [drivers/acpi/thermal.o] Error 1

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>