cpumask: export cpumask_of_cpu_map

fix:

 ERROR: "cpumask_of_cpu_map" [drivers/acpi/processor.ko] undefined!
 ERROR: "cpumask_of_cpu_map" [arch/x86/kernel/microcode.ko] undefined!
 ERROR: "cpumask_of_cpu_map" [arch/x86/kernel/cpu/cpufreq/speedstep-ich.ko] undefined!
 ERROR: "cpumask_of_cpu_map" [arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko] undefined!

Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/cpu.c

@@ -572,3 +572,5 @@ __initdata
 };
 
 const cpumask_t *cpumask_of_cpu_map = cpumask_map;
+
+EXPORT_SYMBOL_GPL(cpumask_of_cpu_map);