thermal: intel_pch_thermal: fix build for ACPI not enabled

thermal: intel_pch_thermal: fix build for ACPI not enabled

The reference to acpi_gbl_FADT causes a build error when ACPI is not
enabled. Fix by making that conditional on CONFIG_ACPI.

../drivers/thermal/intel/intel_pch_thermal.c: In function 'pch_wpt_suspend':
../drivers/thermal/intel/intel_pch_thermal.c:217:8: error: 'acpi_gbl_FADT' undeclared (first use in this function); did you mean 'acpi_get_type'?
  if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
        ^~~~~~~~~~~~~

Fixes: ef63b043ac86 ("thermal: intel: pch: fix S0ix failure due to PCH temperature above threshold")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Sumeet Pawnikar <sumeet.r.pawnikar@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Amit Kucheria <amitk@kernel.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201117023807.8266-1-rdunlap@infradead.org