[CPUFREQ] do not declare undefined functions

fill_powernow_table_pstate() and fill_powernow_table_fidvid() are only
defined and used for X86_POWERNOW_K8_ACPI.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Dave Jones <davej@redhat.com>

arch/i386/kernel/cpu/cpufreq/powernow-k8.h

@@ -215,8 +215,10 @@ static int core_frequency_transition(struct powernow_k8_data *data, u32 reqfid);
 
 static void powernow_k8_acpi_pst_values(struct powernow_k8_data *data, unsigned int index);
 
+#ifdef CONFIG_X86_POWERNOW_K8_ACPI
 static int fill_powernow_table_pstate(struct powernow_k8_data *data, struct cpufreq_frequency_table *powernow_table);
 static int fill_powernow_table_fidvid(struct powernow_k8_data *data, struct cpufreq_frequency_table *powernow_table);
+#endif
 
 #ifdef CONFIG_SMP
 static inline void define_siblings(int cpu, cpumask_t cpu_sharedcore_mask[])