kvm/x86: Fix unused variable warning in kvm_timer_init()

When CONFIG_CPU_FREQ is not set, int cpu is unused and gcc rightfully
warns about it:

  arch/x86/kvm/x86.c: In function ‘kvm_timer_init’:
  arch/x86/kvm/x86.c:5697:6: warning: unused variable ‘cpu’ [-Wunused-variable]
    int cpu;
        ^~~

But since it is used only in the CONFIG_CPU_FREQ block, simply move it
there, thus squashing the warning too.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/x86.c

@@ -5733,13 +5733,13 @@ static int kvmclock_cpu_online(unsigned int cpu)
 
 static void kvm_timer_init(void)
 {
-	int cpu;
-
 	max_tsc_khz = tsc_khz;
 
 	if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
 #ifdef CONFIG_CPU_FREQ
 		struct cpufreq_policy policy;
+		int cpu;
+
 		memset(&policy, 0, sizeof(policy));
 		cpu = get_cpu();
 		cpufreq_get_policy(&policy, cpu);