cpufreq: CPPC: Fix build error without CONFIG_ACPI_CPPC_CPUFREQ_FIE

If CONFIG_ACPI_CPPC_CPUFREQ_FIE is not set, building fails:

drivers/cpufreq/cppc_cpufreq.c: In function ‘populate_efficiency_class’:
drivers/cpufreq/cppc_cpufreq.c:584:2: error: ‘cppc_cpufreq_driver’ undeclared (first use in this function); did you mean ‘cpufreq_driver’?
  cppc_cpufreq_driver.register_em = cppc_cpufreq_register_em;
  ^~~~~~~~~~~~~~~~~~~
  cpufreq_driver

Make declare of cppc_cpufreq_driver out of CONFIG_ACPI_CPPC_CPUFREQ_FIE
to fix this.

Fixes: 740fcdc ("cpufreq: CPPC: Register EM based on efficiency class information")
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cppc_cpufreq.c

@@ -61,6 +61,8 @@ static struct cppc_workaround_oem_info wa_info[] = {
 	}
 };
 
+static struct cpufreq_driver cppc_cpufreq_driver;
+
 #ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE
 
 /* Frequency invariance support */
@@ -75,7 +77,6 @@ struct cppc_freq_invariance {
 static DEFINE_PER_CPU(struct cppc_freq_invariance, cppc_freq_inv);
 static struct kthread_worker *kworker_fie;
 
-static struct cpufreq_driver cppc_cpufreq_driver;
 static unsigned int hisi_cppc_cpufreq_get_rate(unsigned int cpu);
 static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
 				 struct cppc_perf_fb_ctrs *fb_ctrs_t0,