ACPI: arm64: export acpi_arch_thermal_cpufreq_pctg()

The cpufreq code can be in a loadable module, so the architecture support
for it has to be exported:

ERROR: modpost: "acpi_arch_thermal_cpufreq_pctg" [drivers/acpi/processor.ko] undefined!

Fixes: 310293a2 ("ACPI: processor: reduce CPUFREQ thermal reduction pctg for Tegra241")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/arm64/thermal_cpufreq.c

 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/acpi.h>
+#include <linux/export.h>
 
 #include "../internal.h"
 
@@ -18,3 +19,4 @@ int acpi_arch_thermal_cpufreq_pctg(void)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(acpi_arch_thermal_cpufreq_pctg);